CA1058922A

CA1058922A - Fastener system

Info

Publication number: CA1058922A
Application number: CA254,522A
Authority: CA
Inventors: John O. King Jr.
Original assignee: Individual
Current assignee: Individual
Priority date: 1976-06-10
Filing date: 1976-06-10
Publication date: 1979-07-24

Abstract

ABSTRACT OF THE DISCLOSURE

A fastener assembly for connecting together work pieces with aligned holes therethrough of an initial diameter comprising a fastener defining a forwardly facing driving face on the leading end thereof;
a separate expansion member removably and operatively associated with the fastener and defining an outside expansion surface thereon that enlarges out-wardly from a minor expansion diameter at the leading end of the expansion surface to a major expansion diameter larger than the hole diameter, the ex-pansion member defining a rearwardly facing driven face thereon to be engaged by the driving face on the fastener to force the expansion member into the holes; and alignment means for maintaining the fastener and expansion member coaxial as the fastener and expansion member are forced through the holes with the expansion member leading the fastener to expand the holes.

Description

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F~STENL:R SY~TEM

BACKGROUND OF Tl-IE INVENTION

As fastener joints and work pieces have become more highly stressed, especially in the aerospace indus-try, a great deal of effort has been expended in an attempt to produce a joint which has optimum strength together with optimum fatiyue life. The most successful method of increasing the fatigue life of a fastener joint is to generate a compressive stress grad-ient in the work pieces of the joint imnlediate adjacent the holes in the fin-ished joint. One technique which has been used to generate the compressive ~;~
stress gradient is conunonly known as an interference fit where the diameter of the shank of the fastener used in the joint is greater than the nominal diam-eter of the holes in which it is to be fitted. Another technique that has been used to generate the compressive stress gradient is comlnonly known as cold-working wherein the holes through the work pieces are expanded prior to instal-lation of the fastener to such an extent that the metal of the work pieces im~
mediately surrounding the holes where the localized expansion occurs is llon-elastically expanded beyond itsYield point and after which the hole is perlllit-ted to return or rebound toward its original diameter to establ;sh a compres-sive stress gradient immediately surrounding the holes. The fastener is then installed in the holes to complete the joint. Such techniques have also been combined to insure that a prescribed amount of interference fit is obtained upon installation of the fastener.

Because it is desirable to maintain the production ;
costs of a fastener joint at a minimum, fasteners have been ;ntegrally co~
bined with an expansion mandrel to coldwork the holes of the joint and also install the fastener in the holes as a single operation. That portion of the expansion mandrel used to pull the expansion portion through the holes and the -fastener into the holes had to be removed from the fastener before the locking member such as a threaded nut or swagable collar was installed on the fastener.
This has precluded any axial tensile preload from being applied to the fasten-er as the locking menlber was installed. Because these mandrels have been made ~,J ~ ~

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;l jl of one piece, however, it has been difficult to achieve the necessary hardness ¦ in the enlarged portion of the mandrel which contacts and expands the hole while at the same tin1e being able to achieve the necessary toughness in that j portion of the mandrel which is used to pull the mandrel through the hole.
As a result, the prior art has had to resort to the use of exotic lubricants and to the use of sleeve members to isolate the surface of the hole from the expansion surface of the mandrel in order to be able to physically pull the mandrel throuyh the hole and also not damaye the hole.

Il Generally, two types of fasteners are used in fastener l joints. The first type of fastener is a fastener having a substantially con-stant diameter beariny section that is placed through substantially constant ~-l, diameter holes in the work pieces and the second type is a fastener with a -¦ ¦I forward tapered bearing section that tapers outwardly from the engagement ;
section toward the head which is placed in a correspondingly tapered hole ~-~
through the work pieces. While forwarded tapered fasteners do produce fasten-er joints with yood beariny contact between the bearing section of the fasten~
er and the work pieces, the major difficulty with using such fastener systems is that it is extremely difficult to produce the correct tapered hole through I the work pieces. It will also be noted that such tapered fasteners tend to be ¦Iforced out of the holes, head end first, thereby requiring a strong locking device such as a nut or collar to retain the fastener in place. When using a constant diameter bearing section fastener system, the hole forming process is ;~
considerably simplified, however, it is more difficult to obtain good beariny , between the bearing section of the fastener and the work pieces. The require-ment of these prior ar-t systems of a locking device such as a nut or collar has resulted in the systems rennaining relatively heavy thereby reducing the overal1 pay 1Oad oF the structure in which they are used. ~;

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SUMMARY OF T~ E INVENTION

These and other problems and disadvantages associated with the prior art are overcome by the invention disclosed herein by providing an assembly which is able to provide both the cold-working of the holes of a fastener joint and the interference fit of the fastener within the holes in a single operation, which maintains the fastener centered in the holes during installation -to prevent the engagement section on the fastener from contacting the hole walls and damaging them and which combines a two piece expansion mandrel with a fastener so that the expansion portion of the mandrel is separate from the fastener and the support por- ;
tion of the mandrel. ~his maintains a simplified installation procedure to form the fastener joint while permitting the desired hardness to be maintained in the expansion portion of the mandrel and the desired toughness to be maintained in the support portion of the mandrel. Moreover, a variety of different expansion por~
tions may be used and a variety of different type fasteners may be used. Different amounts of coldwoxk may be obtained and a guaranteed axial tension preload may be maintained in the fastener as it is locked in place to form the joint. The fastener may be ~
provided with a reverse taper on at least the leading portion of ~-the bearing section opposite the head which serves to maintain the fastener in place in the work pieces and also clamp the work pieces together.
One aspect of the invention pertains to a fastener assembly for connecting together work pieces with aligned holes .~ , .
therethrough of an initial diameter. The assembly includes a fastener with a fastener central axis, a leading end and a trail-ing end including an elongate bearing section and an enlarged -head section integral with the trailing end of the bearing section, the fastener defining a forwardly facing driving face thereon generally normal to the fastener central axis and leading the bearing section. A separate expansion collet is provided with _3_ :
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an expansion central axis, a leading end ancl a trailing end and defining a collet central passaae therethrough concentric about the expansion central a~is. An ou-tside expansion surface on the collet is concentric about the expansion central axis that en-larges outwardly from a minor ex~ansion diameter smaller than the initial hole diameter a-t the leading end of the expansion surface to a major expansion diameter larger than the initial hole dia-meter trailing the minor expansion diameter. A rearwardly facing ' driven face on the collet is generally normal to the expansion central axis to be engaged by the driving face on the fastener to force the ex~ansion collet through the holes. The assembly further includes an alignment member having a support section positively connected to the leading end of the fas-tener and a pulling section leading the support section and adapted to be en-gaged to pull the fastener assembly into the holes. The support section of the alignment member is adapted to removably fit in the collet central passage to removably support the collet in op-erative association with the fastener so that the expansion central axis of the expansion collet is coaxial with the fastener ~ -central axis with the driving face on the fastener engaging the driven face on the expansion collet to force the expansion collet through the holes ahead of the fastener to expand the holes as the fastener is moved into the holes.
The invention also comprehends methods of installing the fastener assembly which in one aspect comprises the steps of simultaneously exerting a pulling force on the expansion member and a pushing force on the fastener to force the fastener into the holes.
A still further aspect of the invention pertains to a method of forming a fastener joint including the steps of: insert-ing an expansion member in the holes through the work pieces .

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where the expansion member has an expansion section with a major diameter larger than the initial diameter of the holes and a fastener to be installed in the holes is coaxially aliyned with the expansion member so that the leading end of the fastener is at the trailing end of the expansion member exerting a pushing force on the fastener. A pulling force i5 simultaneously exerted on the expansion member to force the expansion member through the holes and the fastener into the holes with the expansion member immediately preceeding the fastener through the holes. ~
More particularly as disclosed, the apparatus of the ~ ' invention includes a fastener which has an elongate bearing section adapted to extend through aligned holes in work pieces with a head ; integral with the trailing end of the bearing section. The leading end of the fastener is provided with a forwardly facing driving face generally normal to the fastener central axis. An expansion collet is removably mounted at the leading end of the fastener by a collet support member which may be integrally or removably connected to the leading end of the fastener and which maintains the collet coaxially aligned with the fastener.

; ' ,-~ -4a-The collet defines an expansion surface thereon to expand the holes throllgh the work pieces as it is forced therethrough immediately preceeding the 1asten-~er. The trailing end of the expansion collet defines a driven face thereon or-iented generally normal to the collet axis that is engaged by the driven face on the fastener to force the collet through the holes.

The fastener bearing section may have a reverse l;apered section thereon and tapers inwardly from the leading end of the bearing section toward its trailing end so that when the holes through the work pieces are ¦ expanded to allow the fastener to be installed the holes recover to a diameter !O ¦ smaller than the major diameter of the bearing section to create an interfer-i ence fit. The compressive force gradient about the holes act on the bearing surface on the beariny section of the fastener to force the work pieces toward each other to clamp them together so that the work pie-ces themselves serve to lock the fastener in place and reduce or eliminate the external force re-quired to retain the fastener in the holes.

The expansion collet may be separate or integral with the collet support member so long as it is separate and removable from the ¦ fastener. The collet has a pilot surface which maintains the collet coaxial I with the holes and an expansion surface trailing the pilot sur~ace to expand ,0 the holes. The collet may be a solid member or a wire coil member.

The collet support member may be made in the form of a pintail to pull the fastener into the holes and thus the expansion collet through the holes. The pintail may also be used to axially tensile preload the ~- -fastener when it is positively connected to the fastener.

¦ These and other features and advantages of the inventior j disclosed herein will become more apparent upon consideration of the followingspecification and accompanying drawings wherein like characters of reference will designate corresponding parts throughout the several views and in which:
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E~CR.~ N OF TIIE DRAWINGS

Fig. 1 is an exploded elevational view showing a first embodiment of the inventioni Fig. 2 is an exploded elevational view of a second em-bodiment of the invention;
~ : -Fig. 3 is an exploded elevational view of a third em-bodiment of the invention;

Fig. 4 is an exploded elevational view of a fourth em-bodiment of the invention;
Fig. 5 is an exploded elevational view of a fifth em-bodiment of the invention; ~1 , Fig. 6 is an enlarged side elevational view shown partly in cross-section of the streamline collet of Fig. l;

Fig. 7 is a leading end view of the collet of Fig. 6;

Fig. 8 is a trailing end view of the collet of Fig. 6; -~

Fig. 9 is an enlarged side elevat;onal view shown ¦
partly in cross-section of the collet of Fig. 2; ¦
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Fig. 10 is an enlarged longitudinal cross-sectional view of the wire coil collet of Fig. 3;

~0 Fig. 11 is a partial enlarged side elevational view of the colle oF Fig. 4;

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Fig. 12 is an enlarged side elevational view of the pintail connector on the fastener of Fig. 5;

Fig. 13 is an enlarged side elevational view of ~he trailing end of the pintail of Fig. 5;

Fig. 14 is an enlarged side elevational view of a modified pintail connector on the fastener of Fig. 5;

Fig. 15 is an enlarged side elevational view of the pintail of Fig. 5 in modified form;

Fig. 16 is a view showing the invention of Fig. I
ready for use;

Fig. 17 is a view similar to Fig. 16 showing the in-` vention of Fig. 1 being used;

Fig . 18 is a view sinnilar to Fig. 1~ showing the fastener of the invention of Fig. 1 in placei Fig. 19 is an elevational view partly in cross-section ; showing the preload adapter of the invention in use with the fastener of Fig.
18 to finally install same;
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Fig. 20 is an operating end view of the preload adapter of Fig. 19;

Fig. 21 is a schematic view of the tool for carrying out the method of the invention;
:'' : , Fig. 22 is a cross-sectional view of a joint using the invention of Figs. 2 and 9, appearing with Figs. 15-20;

Fig. 23 is a cross-sectional view showing the inven-tion of Figs. 3 and 10 being installed; ;
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Fig. 24 is a cross-sectional view showing the inventionl oF F;gs. 5 and 12-15 being installed;

Fig. 25 is a cross-sectional view showing a hole clean-ing attachment for the invention;
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Fig. 26 is a cross-sectional view illustrating the hole cleaning attachment oF Figs. 25 in use; and, Fig. 27 is a longitudinal cross-sectional view of an installation tool for the embodiment of Fig. 5.

These figures and the following detailed description .o ¦ disclose specific embodiments of the invention, however, it is to bP under-stood that the inventive concept is not limited thereto since it may be em-bodied in her forms.

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DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

It will be seen from the drawings that each embodiment of the invention includes a fastener F, an expansion collet C, and a col',~et support S connected to the leading end of the fastener F and mounting the collet C coaxial with the fastener at the leading end thereof. In this n~anner,the fastener F forces the collet through the holes in the work pieces to cold -work the holes as the collet C is forced therethrough immediately preceeding the fastener F. : -.~; ?
Referring now to Fi gs . 1 and 6-8, the fastener F has been designated 10, the collet support S is illustrated as a pintail 12 and the collet C has been designated 11. The fastener 10 has a bearing section 14 adapted to extend through holes H in work pieces P as seen in Figs. 16-1~, an engagement section lS integral with the leading end of the bearing section 14 and coaxial therewith about the pin axis Ap, and an enlarged head 16 integral with the trailing end of the bearing section 14~ The bearing section 14 has , a diameter dB adapted to extend through holes H through the work pieces P after , they have been expanded as seen in Figs. 16 and 17. The diameter dB iS gen- ';
erally smaller than the major expansion diameter of col1et 11 and may be var-;ed depend;ng on the amount of interference which is desired between the work pieces and the fastener after installation as will become more apparent. The leading end of the bearing section 14 is connected to the trailing end of the '~ ,;
engagement section 15 through a,lead-in section 18 normally associa~ed with '~
threaded fasteners. The engagement section 15 at the leading end of the fasten- 1~, er is illustrated with conventional threads 19 to receive a conventional nut as will become more apparent. It may similarly be provided with locking grooves , '~
¦ to receive a swagable locking collar. The engagement section 15 has a major ¦ ,''~
thread crest diameter dTC slightly smaller than the bearing~diameter d~ as is l "-normally associated with fasteners. It will also be noted that the threads 19 ~

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have a smaller root diameter dTR as best seen in Fig. 1. The leading end of engagement section 15 defines a forwardly facing annular driving face 20 con-centric about and normal to axis Ap. The dr;ving face 20 has an outside diameter at least as small as the root diameter dTR of the threads 19 as will become more ~pparent.

The pintail 12 is integrally connected to the leading end of the engagement section 15 of the fastener 10 through a grooved frangi- ¦ble breakneck section 21 so that pintail 12 is concentric'about axis Ap.
Pintail 12 has a pulling section 22 at the leading end thereof and an integral support section 24 at the trailing end thereof. The support section 24 de-fines a cylindrical support surface 25 thereon concentric about axis Ap which supports the collet 11. The surface 25 has a length LSs and a diameter d55 smaller than the thread root diameter dTR amd substantially equal to the in-side diameter of the collet 11 as will become more apparent. The pulling section 22 includes alternate lands 26 and grooves 2B which are adapted to be gripped by a conventional lockbolt installation gun as will become more ~ppar-ent. The pulling section 22 has a major outside diameter dp5 at least as small as the diameter d5S but may be a prescribed amount smaller than diameter dSS to insure that the collet 11 can be removed from pintail 12 after h'o'le expans;on as will become more apparent.
~' The collet 11 is removably carried on the support , section 24 and includes a seamless annular side wall 30 concentric about the , ,' collet central axis Ac. The collet 11 has a leading end 31 and a trailing end 32. Side wall 30 defines a cylindrical central passage 3~ therethrough with -~a diameter dcp which is just sufficient for collet 11 to be slidably received -~
onto the support surface 25 of pintail 16 and b'e in bearing support thereon.
The diameter dcp is usually no more than 0.001 inch greater than diameter d of support surface 25. The collet 11 has a length Lc substantially equal to the sum of length LSS f support section 24 and the length of breakneck section ' I'2i. .

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~o~zz The side wall 30 includes a leading pilot section 35 and a trailing expansiGn section 36. The pilot section 35 defines a cylindri-cal pilot surface 3~ on the outside thereof concentric about the collet central axis Ac. Pilot surface 3~ has a length LpC and a diameter dpC sufficient to locate the collet 11 coaxially with the centerline of the holes H through the work pieces P as seen in Fig. 16 when surface 38 extends into holes H. Nor-mally, diameter dpC of pilot surface 38 is in the order of 0.001 inch less than the intial hole diameter DHI and the length LpC is at least one bearing ~-diameter of the fastener 10.

Expansion section 36 includes a leading expansion sur-face 40, an intermediate land surface 41, and a trialing contraction sur~ace 42, all concentric about the central axis Ac of collet 11. The expansion surface 40 flares outwardly from the pilot diameter dpC to a major expansion diameter dEM at its trailing end greater ~han the initial hole diameter DHI
by that amount which it is desired to expand holes H. If cold~orking is de-sired, diameter dEM iS usually 2-10% greater than the hole diameter DHI depend-ing on the material of the work pieces P and the final hole diameter DHF seen in Fig. 18 desired. The expansion surFace 40 is semi-ellipsoidal in shape where the included angle between the trangent to surface 40 at any point de-creases from the leading to the trailing end of surface 40. ~t will be seen that such shape for surface 40 produces an exponentially increasing mechanical advantage at the surface 40/hole interface from the leading to the trailing end of surface 40. This serves to minimize the frictional interface between the ;
surface 40 which, in turn, reduces the force required to move the surface 40 .
through the holes H. Because the radial expansion forces required to expand the holes H increase exponentially with the amount of expansion, the exponen- ~ ;
tially increasing mechanical advantage of surface 40 offsets the increasing ~;-expansion forces required to reduce pulliny force necessary, to move the surface40 throug oles H.

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The land surface 41 is cylindrical with the major expansion diameter dEM and a convenient length which allows the surface 40 to be reground without reducing diameter dEM. Ilowever, i~ will be noted that the length of land surface 41 will be shortened each time the expansion surface 40 ¦ is reground~ The leading end of land surface 41 is joined to expansion sur-face ~0 through a smooth transition surface ~4.

The contraction surface 40 tapers inwardly from the major expansion diameter dEM at its leading end and a minor contraction dia-meter dCM at its trailing end. The diameter dCM is usually about equal to the LO bearing diameter dB. While different shapes may be used for surface 42~ it is illustrated as frusto-conical defining an included angle with the axi~ Ac less than the average included angle between the tangents to surface 40 and the axis Ac. The leading end oF surface 42 is joined to land surface 41 through a smooth transition surface 45. As the compressive forces ~ending to ' force the holes H closed toward the recovered hole diameter DHR are applied ¦ against the contraction surface ~29 these forces tend to force the expan~ion ~section 36 through the holes H. This also results in reducing the pulling I force required to move the section 36 through the holes.

¦ The trailing end of the annular side wall 30 defines ~20 a rearwardly facing annular driven face 50 concentrically located with respect to the axis Ac and lying in a plane normal thereto. The surface 50 has an out-side diameter dCF which is at least as small as the root diameter dTR f threads 19 on fastener 10 that is adapted to be engaged by driving face 20 of the fastener 10 as will become more apparent. The trailing end oF side wall `30 further defines a clearance surface 51 joined to the peripheral edge of the driven face 50 and extending forwardly and outwardly therefrom at a suffi-cient clearance angle with the plane of face 50 to provide clearance for the ~-leading thread 19 of the fastener 10 so that the driven face 50 will not . . . ' . -' : . :
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~5~39~'2 I l distort this leading thread when the co11et is forced -through the holes. The clearance angle may be varied as required to prevent damage to the leading thread 13 of the fastener, however, an angle of 5-15 is usually sufficient.
The outer periphery of the clearance surface 51 joins with the trailing end of contraction surface 42 through a smoothly rounded corner surface 52. The col-let 11 may be provided with a clearance counterbore 54 as best seen in Fig. 6 at the trailing end of passage 34 to provide a clearance over the groove(l breakneck section 21 connecting the pintail 12 to fastener 10. The length of the counterbore 54 is approximately the length of breakneck section 21 so that ~ s the collet 11 can be removed from pintail 12 even if the unsupported trailing end of collet 11 is slightly contracted during the expansion of the holes H.
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Because the operator who pul1s the fastener 10 into the holes H and the collet 11 through the holes works from the off side OS of the work pieces P as seen in Fig. 16 while the collet 11 is initially located on the near side NS of the work pieces, some indication is desired as to whether the pilot section 35 has entered the holes. Fig. 16 shows an indicator which assures the operator that the pilot section 35 has entered the holes.
The fastener 10 has a known grip range which varies from a minimum grip Gl to a maximum grip G2 as seen in Fig. 17. It will further be noted that the length LpC of the pilot section 35 is greater than the grip range (G2-Gl) of fastener 10 since the grip range is usually in the order of 1/16 inch for smaller ~ 1 diameter fasteners 10. A distingu;shing ind;cator band 55 is provided on the pulling section 22 of pintail 12 starting a distance Dl forward of the driving face 20 against which collet 11 bears. Distance Dl is equal to the sum of length 10 of the expansion section 36 on collet 11, the maximum grip G2 f fastener 10, and a small amount to be visually displayed at maximum grip but less than the sum of the total length Lc of collet 11 and the minimurn grip Gl.
Thus, hen the pilot section 35 on collet 11 is seated in hples ~I with the :, ".: ' . , . .

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l . l driving face 20 on fas-tener 10 beariny ayainst the driven face S0 on collet 11 as seen in Fi9. 16, the leading end of the indicator band 55 ;s visible on the off side OS of work pieces P. If the pilot section 35 is not seated, then the indicator band 55 is not visible on the off side of the work pieces. In this manner, the operator can visually tell if the fastener 10 is ready to be pulled. The indicator band 55 can be painted, coated or otherwise formed on the pulling section 22. This concept could likewise be applied to any drive member incorporating a fastener.

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i SECOND EMBODIMENT

, Referring now to Figs. 2, 9 and 22, the fastener F has been designated 110, the collet support S is illustrated as a pintail 11~ and ':
the collet C has been designated 1l1. The fastener 110 has a bearing section 114 with pin axis Ap adapted to extend through holes l-J in work pieces P as seen in Fig. 20 and an enlarged head 116 integral with the trailing end of the bearing section 114. The bearing section 114 defines an external bearing surface 115 thereon which is concentrically arranged about the axis Ap. The ., bearing surface 115 has a reverse taper subsurface 115R that tapers inwardly from the leading end of the bearing section 114 toward the trailing end thereof.
While the reverse taper subsurface 115R may extend along the entire length of the bearin~ section 114, it is illustrated in Fig. 2 With a length LRT which is approximately equal to the thickness to of the off side work piece P dS .
seen in Fig. 22. While that portion of the bearing surface 115 trailing sub- :
surface 115R may be of constant diameter, it is shown as a forward taper sub-surface 115F in Fig. 2 that tapers outwardly from the trailing end of sub-surface 115R to the head 116 with a length LFT about equal to the thickness tn of the near side work piece P as seen in Fig. 22. The reverse taper sub- ~', , surface 115R tapers uniformly inwardly from the leading major bearing diameter ., dBL at the lead;ng end of the bearing section 114 to an intermediate minor :' bearing diameter dBI at the trailing end of the subsurface 115R. The trailing :1 forward taper subsurface 115F tapers uniformly outwardly from the intermediate ~' diameter dBI to a trailing secondary major bearing diameter dBT at the trailing end of the subsurface 115F. The diameter dBT is larger than diarneter dBI and .
is usually smaller than the major expansion diameter of,collet 111 used to in- .-stall fastener 110. The fastener 110 is installed by expanding the holes and inserting the fastener in the holes so that the material',of the work pieces P '.

about the holes H will contract or rebound into bearing contact with the reverse taper subsurface 115R and the forward taper subsurface 115F to main- :.
taln.,the work pieces P clamped together as will become more apparent.
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The pin-tail 112 is integrally connected to the l~ading ¦
end of the bearing section 114 of the fastener 110 throuyh a grooved frangible breakneck section 121 so that pintail 112 is concentric about axis Ap. ~in-tail 112 has a pulling section 122 at the leading end thereof and an integral support section 124 at the trailing end thereof. The support section 124 de-fines a cylindrical support surface 125 thereon concentric about axis Ap which supports the collet 111. The surface 125 has a length Lss and a diameter d55 smaller than the leading diameter dBL of the bearing section 114 and substartially equal to the inside diameter of the collet 111 as will become more apparent. The pulling section 122 includes alternate lands 126 and grooves 128 which are adapted to be gripped by a conventional lockbolt installation gun as will become more apparent. The pulling section 122 has a major outside diameter dpS at least as small as the diameter d5Sbut may be a prescribed ~;
amount smaller than diameter d55 to insure that the collet 111 can be removed from pintail 112 after hole expansion as will become more apparent.

The collet 111 best seen in Fig. 9 is remcvably re-ceived on the pintail 112 and supported by the support section 124 to eY~pand the holes through the work pieces immediately preceeding the bearing section 114 as the fastener 110 is installed. The collet 111 has an annular s7de wall 130 concentric about the collet central axis Ac with a leading end 131 and a trailing end 132. The side wall 130 defines a cylindrical passage 34 therethrough with a diameter dcp which is just sufficient for the collet 111 ¦
to be slidably received onto the support surface 125 oF the pintail 112 and be in hearing support thereon. The diameter dcp is usually no more than 0.001 inch greater than the diameter dSS of the support surface 125. The collet 111 has a length LC which is substantially equal to the sum of the length of the support se irn 124 and the breakneck section 121.

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58~2~ 1 l ~ i -The side wall 130 includes a ledding pilot section 135 jand a trailing expansion section 136 integral with the trailing end of the pilot section 135. The pilot section 135 defines a cylindrical pilot surface 138 on the outside thereof concentric about the collet central axis Ac. The pilot surface 13~ has an outside diameter dpC which is sufficient to locate the ;~
collet 111 coaxially with the centerline of the holes through the work pieces when the surface 138 extends into the holes as will become more apparent. "
Normally, the diameter dpC of the pilot surface 138 is in the order of 0.001 ~ ~
inch less than the initial hole diameter dHI as will be explained. , ;

o The expansion section 13~ includes a leading expansion ,, surface 140, an intermediate land surface 141 and a trailing contraction sur- ",~
face 142~ all concentric about the central axis Ac of the collet 111. The ex-; pansion surface 140 extends outwardly from the diameter dcp of the pilot sur-,, face 138 to a major diameter dE~l at its trailing end greater than the initial hole diameter through the work pieces by the amount which it is desired to ex-pand the holes. It will be noted that the diameter dEM at least is as great ~' as the leading major diameter dBL of the bearing section 114 as will become ~ ,more apparent. If optimum coldworking is desired, the diameter dEM is usually --2-10% greater than the hole diameter of the initial hole diameter through the ~ , ~0 work pieces as set forth by known data and depends on the material of the work ;
~ieces and the desired final diameter of the holes. While different shapes may be provided for the expansion surface 140, the surface 14nillus~rated is semi-ellipsoidal in shape to produce an exponentially increas;ng mechanical advantage at the surface 140/hole interface from the leading to the trailing ~
, ¦¦ end of the surface 140. The land surface 141 is cylindrical with the maximum ' expansion diameter dEM and is smoothly joined to the expansion surface 140 at , its leading end through surface 144. The contraction su,rface 142 is smoothly joined to the trailing end of the land surface 141 and tape~s inwardly from ~`
t e dia~e er dEM ~ the land surface 141 to a trailin, minor diameter d ;

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which is dt least as large as the leading mAjor diameter d~L on the bearing section 114 of fastener 110 as will becorne more apparent. The trailing end of the side wall 130 defines a rearwardly facing annular driving face 150 thereon which is concentrically located about the axis Ac and lies in a plane normal to the axis. The trailing driven face 150 on the collet 111 is adapted to be engaged by the leading driving face 120 on the bearing section 114 of the Fastener 110 to cause the collet 111 to be forced through thè hoies in the work pieces by pulling on the pulling section 122 of the pintail 112.

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5~g~:2 I THIRD EMBODIME~IT

¦ Referring now to Figs. 3, 10 and 24, the fastener F
¦ has been designated 210, the collet support S is illustrated as a pintail 212 ¦ and the collet C has been designated as a wire coil member 211. The fastener 110 h~s a bearing section 214 aclapted to extend through holes H in work pieces ¦ P as seen in Fig. 24, an engagement section 215 integral with the leading end ¦ of the bearing section 214 and coaxial therewith about the pin axis Ap, qnd an enlarged head 216 integral with the trailing end of the bearing section 214.¦¦ The bearing section 214 has a diameter dB adapted to extend through holes H
~lO ¦ through the work pieces P after they have been expanded as seen in Fig. 24. ~;
~, ¦ The diameter dB iS generally smaller than the major expansion diameter ot ¦ collet 211 and may be varied depending on the amount of interference which is ¦ ;
¦ desired between the work pieces and the fastener after installation as will ¦ become more apparent. The leading end of the bearing section 214 is connectedto the trailing end of the engagement section 215 through a lead-in section ¦ 218 normally associated with threaded fasteners. The engagement section 215 ¦ at the leading end of the fastener is illustrated with conventional threads 219~ ;
¦ to receive a conventional nut as will become more apparent. It may similarly I
¦ be provided w;th locking grooves to receive a swagable locking collar. The ¦ engagement section 215 has a major thread crest diameter dTC slightly smaller ¦ than the bearing diameter dB as is normally associated with fasteners. Tt ¦ will also be noted that the threads 219 have a smaller root diameter dTR as ¦ best seen in Fig. 3. The leading end of engagement section 215 defines a for~¦ wardly facing annular driving face 220 concentric about and normal to axis Ap. ¦ ;
¦ The driving face 220 has an outside diameter at least as small as the rootdiameter d ~ of the threads 219 as will become more apparent.

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j The pintdil 212 is in-tegrally connected to the leading ¦ end of the engagement section 215 of the fastener 210 through a grooved frang-ible breakneck section 221 so that pintail 212 is concentric about axis Ap.
Pintail 212 has a pulling section 222 at the leading end thereof ancl an integral support section 224 at the trailing end thereof. The support section 224 de-1 fines a support surface 225 thereon which b~th supports the coil member 211 !I and determines its outside shape as will become more apparent. It will be seen !that the support surface 225 has a length LsS which is generally equal t~ the I length Lc f the coil member 211 and is frusto-conical in shape tapering out-1, wardly from a leading minor diameter dSL to a trailing major diameter dSr as il will be e~plained. The diameter d5T is smaller than the thread root diameter¦ dTR to provide clearance on face 220. The pulling section 222 i ncludes alter- ¦ -¦ nate lands 226 and grooves 228 which are adapted to be gripped by a conventional~lockbolt installation gun as will become more apparent. The pulling section 222 has a major outside diameter dpS at least as small as the diameter dSL but may be a prescribed amount smaller than diameter dSL to insure that the coil member 211 can be removed from pintail 212 after hole expansion as will become ¦ more appar t.

I I The coil member 211 i ncludes a plurality of in~er-c~nnected helically arranged flights 230 dS iS nOrn1ally associated with springs.
It will be seen that the trailing end 231 of the coil member 2ll is ground flat to define a driven face 250 thereon to be engaged by the forwardly facing driving face 220 on the leading end of the engagement section 215. Each of the flights 230 has a generally circular cross-sectional shape of a diameter ¦ -¦ dCS as seen in Fig. lO. The flights 230 are made out of a strong resilient I ;
material such as spring tempered steel so that flights 230 may be resiliently expanded in order that the coil member 21`1 can be forced onto the support section 22~ of the pintail 212. It will thus be seen that,each of the flights 230 has a normal relaxed inside diameter dc~ which is less than the diameter 11 ' . ' ' ' ;, . , :

to which it is to be expanded. Thus, when the coil member 211 is placed on the pintail 212, at least some of the flights 230 will engage the suppor1:
surface 225 forward of the point at which it will finally rest when the ~oil member has been expanded. As the pintail 212 is gripped and pulled through the holes H in the work pieces P, it will be seen that the engagement between the coi1 member 211 and the work pieces P will force the coil member 211 up along the support surface 225 until the driven face 250 on the coil member 211 engages the driving face 220 on the engagement section 215 as seen in Figs. 10 and 22. In this position, it will b~ 5~en that the leadingmost helical flight 2301 of the coil member 211 is expanded to the outside diameter dpC
substantially equal to the initial hole diameter DHI to act as a pilot, l:he next trailing flight 2302 is expanded to a slightly greater outside diameter dE
the next trailing flight 2303 is expanded to a slightly larger outside diameter dE2 and the final trailing flight 23~4 is expanded to the slightly greater ; maximum expansion outside diameter dEM. The outside diameter dEM is greater than the initial hole diameter DHI by the amount which the holes are to be ex-panded. Thus, it will be seen that the outermost points on each of the helical -flights 230 define an overall expansion surface which tapers outwardly from flight ~301 through flight 2304. Thus, as the coil member 211 is forced through the holes, the dr;ving face 220 on the leading end of the engagement section 215 keeps the flights 230 in a relative stationary position to cause the coil member 211 to expand the holes as seen in Fig. 22. Once the flights 230 have passed through the holes, however, the coil member 211 can be easily I moved from the support section 224 by passing the coil member 211 forwardly ¦ over the pulling section 222 and remove it. The total outside diametrical difference between the diameter dpC and dEM is established by the size of the support surface 22S and the overall general expansion shape of the coil member 211 is established by the shape of surface 225. This allows the same coil member to be used with different size support surfaces 225. ~:
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10589Z~

By properly sizing the flights 23n of the coil member 211, the coil menlber 211 can be screwed onto the threads 219 of khe fastener 210. This allows the engagement section 215 of the fastener 210 to act ~s the support. Because standard threads on fasteners have smaller diameter lead-in thread diameters, these smaller diameter lead-in threads produce an overall generally tapered expansion surface on the coil member so that it can be used to expand the holes. Likewise, the cross-sect-ional shape of the flights 230 can be changed to produce the same effect. Each of the fliyhts 230 may have a slightly larger mean inside diameter (not shown) than the next adjacent leading flight so that the coil 211 will taper outwardly from its leading to trailing d.

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¦ FOURT~I EMBODIMENT
': l Referring now to Figs. 4 and 11, the fastener F has been designated 310, the collet support S and the collet C are shown as ~n in-tegral guide member 311 separate from fas-tener 310. The fastener 310 has a bearing section 314 adapted to extend through holes H in work pieces P, an engagement section 315 integral with the leading end of the bearing section 314 and coaxial with the pin aY~is Ap, and an enlarged head 316 integral with the trailing end of the bearing section 314. The bearing section 314 has a diameter dB adapted to extend through holes H through the work pieces P after they have been expanded with the guide member 311. The diameter dB is generall~
smaller than the major expansion diameter of guide member 311 and may be varied depending on the amount of interference which is desired between the work:
pieces and the fastener after installation as will become more apparent. The ;~
¦ leading end of the bearing section 314 is connected to the trailing end qf the¦ engagement section 315 through a lead-in section 318 normally associated with `-threaded fasteners. The engagement section 315 at the leading end of the ~astener is illustrated with conventional threads 319 to receive a conventional nut as will become more apparent. It may similarly be provided with loching grooves to receive a swagable locking collar. The engagement section 315 has ¦
a major thread crest diameter dTC slightly smaller than the bearing diameter dB as is normally associated with fasteners. It will also be noted that the threads 319 have a smaller root diameter dTR as best seen in Fig. 4. The leading end of engagement section 315 defines a forwardly facing annular driving face 320 concentric about and normal to axis Ap. The driving face 320 - has an outside diameter at least as small as the root diameter dTR of the threads 319 as will become more apparent. The :leading portion of the engage-ment section 315 is provided with a guide passage 321 which opens onto the leading end of engagement section 315 and which is concentric with axis Ap as .. . .

ll i seen in Fi . 11. The p~ss~ge 321 may be broache~ int~ an intern~1 socket with internal wrenchiny surfaces 317 along its lenyth. The wrenching surfaces 317 would have a minor diameter opening dGM as seen in Fig. 11. The passage 321 ::
may be countersunk to provide a lead-in thereto. The annular driving face 320, then, is defined outboard of the countersink.
' The guide member 311 has a pulling section 322 at the leading end thereof, an intermediate expansion section 325 integral wlth the trailing end of the pulling section, and an integral support section 324 at the trailing end thereof concentric about common axis Ac. The pulling section 322 includes alternate lands 326 and grooves 328 which are adapted to be gripped by a conventional lockbolt installation gun as will become more apparen~.
The pulling section 322 has a major outside diameter dpS such that the pulling I ~-section is slidably received through the initial diameter holes in the work ~
pieces. The expansion section 325 includes a cylindrical pilot portion ~35 .
concentric about the axis Ac adjacent the leading end of the expansion section 325 with an expansion portion 336 concentric with respect to the axis Al in-tegral with the trailing end of the pilot portion 335. The pilot portion 335 defines a cylindrical outside pilot surface 338 thereon of a diameter dp~.
- The diameter dpC is just slightly less than the initial nominal hole diameter DHI through the work pieces P so that the pilot portion 335 will just slidably pass into the initial holes H to center the axis Ac on the centerline of the holes H. The length of the pilot portion 335 is sufficient to support the guide member 311 against cocking as it is forced through the holes H in the ~ ~
work pieces. ~ ~;

The expansion portion 336 defines an outwardly tapering expansion surface 3~0 thereon which tapers outwardly from the diameter dpC at its leading end toward the trailing end thereof. The expansion surface 340 is illustrated as frusto-conical, however, it is to be understood that other , ' . ,,i ".: . , , , , , . . , ~, ;

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l l shaped surfaces may be used. The leading end of the expansion surface 3~0 is smoothly joined to the pilot surface 335. The surface 340 has a major expan-sion diameter dEM at the trailing end thereof which is a prescribed amount larger than the intial diame-ter D~l~ of the holes H through the work pieces.
The amount that diameter dEM is larger than the diameter DHI is determil~ed by the amount it is desired to enlarge the diameter of the holes as the guide member 311 passes therethrough. The expansion portion 336 Further includes ; a generally cylindrical land surface 341 with diameter dEM smoothly joined to the trailing end of surface 341. The trailing end of the expansion portion 336 defines a rearwardly facing driven face 350 thereon generally normal to axis Ac. The outer periphery oF the bearing face 350 joins with the trailing end of land surface 341 through a smoothly curved contraction surface 342 over which the expanded material about the holes H recovers when the guide member 311 passes through the holes as will be come more apparent.
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The support section 324 includes a projection 345 de-fining an outside cylindrical locating surface 346 thereon concentric about ¦ the axis Ac with an outside diameter dpo that fits within the passage 321 in ¦ the fastener 310 as will become more apparent. It will further be noted that the section 324 projects rearwardly of the driven face 350 a prescribed dis- ¦
~0 ¦ tance LpO as will become more apparent. To install the fastener 310, pro~
Il jection 345 on guide member 311 as best seen in Fig. 11 is inserted into pas-¦¦ sage 321 so that the projection surface 346 is in bearing contact with thewrenching surfaces 317 in passage 321. The projection 345 serves to maintain the fastener 310 coaxial, with the guide member 311 so that the Fastener 310 can be installed. It will also be noted that projection 345 may be remo~ably attached to the rest of guide member 311.

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FIFTH EM13ODIMF.NT
., Referring now to Figs. 5, 12, 13 and 24, the fas~ener F has been designated 410, the collet support S is illustrated as a separate pintail 412 and a pintail connector 460 integral with fastener 410, and the collet C has been designated 11. The fastener 410 has a bearing section 414 adapted to extend through holes H in work pieces P as seen in Fig. 24, an engagement section 415 integral with the leading end of the bearing sectlon 414 and coaxial therewith about the pin axis Ap, and an enlarged head 416 integral with the trailing end of the bearing section 414. The bearing ~ection 414 has a diameter dB adapted to extend through holes H through the work pieces P after they have been expanded as seen in Fig. 24. The diameter dB is gen~
erally smaller than the major expansion diameter of collet 411 and may be var-ied depending on the amount of interference which is desired between the work pieces and the fastener after installation as will become more apparent. The I ~
leading end of the bearing section 414 in connected to the trailing end of the I - :
engagement section 415 through a lead-in section 418 normally associated with threaded fasteners. The engagement section 415 at the leading end of the fastener is illustrated with conventional threads 419 to receive a conventional nut as will become more apparent. It may similarly be provided with locking grooves to receive a swagable locking collar. The engagement section 415 has a major thread crest diameter dTC slightly smaller than the bearing diameter dB as is normally associated with fasteners. It will also be noted that the threads ~19 have a smaller root diameter dTR as best seen in Fig. 1~. T~!e leading end of engagement section 415 defines a forwardly facing annular driving face 420 concentric about and normal to axis Ap. The driving face 420 has an outside diameter dDE at least as small ~s the root diameter dTR ot the threa.s 4 as will become more apparent.

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The pintail connector 460 is integral with the leading il end o~ the engagement section 415 and provides a means by which the fastener 410 can be releasably connected to the pintail 412. The pintail connector 460 is best seen in Figs. 5 and 12 and includes a generally semi-cylindrical body 461 defining an arcuate peripherial support surface 462 thereon having ¦ a radius RpC centered on axis Ap so that the surface 462 is coaxial with axis Ap. The opposite ends of the arcuate surface 462 are joined by a flat surface 464 which lies along a chord of the cylinder defined by the radius PpC 50 that - the longitudinal axis of surface 464 is generally parallel to the fastener 0 axis Ap. The surface 464 is located so that the maximum height hM between ~`lat surface 464 and arcuate surface 462 when measured perpendicular to sur- ¦
face 464 is greater than the radius RpC as will become more apparent. The body 461 has a length Lp~ also to become more apparent. Body 461 also has a transversely extending recess 465 thereacross which opens onto the flat surface 464. Recess 465 has a bottom edge 466 generally parallel to the flat surface 464 and a leading push edge 46~ extending from the flat surface 464 to the bottom edge 466 and forming a shoulder 469 on body 461. The push 1~ edge 468 is located a distance dpE rearwardly of the leading end 47~ of body 461 and the recess 465 has a depth dpR so that that portion of body 461 span-~o ning the recess 465 has a maximum thickness tM when measured perpend;cular to bottom edge 466 of recess 465. The recess 465 has a length LpR such that the rear edge o~ the recess 465 is the leading end of the engagement section 415.
The radius RpC is less than one-half the thread root d;ameter dTR 50 that an annular driving face 420 is defined on the leading end of engagement section 415 between the arcuate surface 462 on body 461 and the root of the leading I thread 419.

¦ The pintail 412 is an elongate and generally cylindri-I cal member with a central axis AT. The pintail 412 as bes~ seen in Figs.
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13 and 15 has a generally cylindrical support section 424 at its trailing end and a pulllng section 422 at its leading end which can be engaged by a lock-bolt installa~ion gun to pull the pintail through the holes o~ the work pieces as will become more apparent. The overall length of the pintail 412 is greater than the thickness of the work pieces as will become more apparent so that the leading end of the pinta-il will project through the holes in th~ work pieces prior to installation. The support section 424 of the pintail 41'~ is a cylindrica'l section defining a generally cylindrical peripheral support surface 425 thereon with a diameter dSS substantially equal to twice the radius PpC of the surface 462 on the pintail connector 460. The support ~ ' section 424 has length LSs which is sufficient to support the collet 411 as ,'will become more apparent. The trailing end of the support section 424 is provided with a cutout 471 which extends ~orwardly from the trailing end of the section 4?4. The cutout 471 has a length Lco substantially equal to the length of the pintail connector 460 as will become more apparent. The cutout 471 has a depth dCo substantially equal to the maxi-mum thickness tM of that -~
portion of the pintail connector 460 span~ing the recess 465. Cutout 477 de- ~' fines a generally flat inside surface 472 on the support section 424 which lies along a chord of the support section 424 so tha~ the longitudi'nal axis of surface 472 is generally parallel to the pintail axis AT. The surface 472 is located so that the maximum height hpM between the flat surface 472 and the ¦cylindrical surface 425 when measured perpendicular to surface 472 is greater than one-half the diameter dSS o~ the support section 424. A transversely ex-tending recess 474 is provided across the support secti,on 424 and opens onto -the flat surface 472. The recess 474 has a bottom edge 475 generally parallel to the flat surface 472 and a trailing pull edge 476 extending from the flat surface 472 to the bottom edge 475 and forming'a shoulder 47~ on the support ,`'' section 424 adjacent the flat surface 472. The pull edge 476 is located a distance dpE forwardly of the trailing end of the support section 424 and I
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the recess 474 has a depth cl~p so th~t that portion of the support section 424 spanning the recess 474 has a maximum thickness tpM measured perpendicular to the bottom edge 475 of the recess 474. The recess 474 has a length LpM such that the leading edge of the recess 474 is a continuation of surface 479 at the leading end oF the cutout 471. The surface 479 is perpendicular to the pintail axis AT.

When the shoulder 47~ on the support section 424 of the pintail 412 is inserted into ~he recess 465 on the pintail connector 460 as seen in Fig. 24, the push edge 468 on the connector 460 will be aligned with the pull edge 476 on the pintail 412 so that the fastener 410 can be pulled into position in holes through work pieces by pulling on the pintail 412. In this position, it will be noted that the cylindrical surface 425 on the supportlsection 424 of the pintail 412 forms a continuation of the support surface 462 ¦on the pintail' connector 460 so that the resulting combination has an eft'ective diameter dSS over which the collet 411 can be slidably received and supported thereon. ~he collet 411 also serves to positively lock pintail 412 on con-nector 460 to maintain fastener 410 and pintail 412 coaxial. ~ I

The pull section 422 on the pintail 412 as seen,in Fig.
5 is provided with an appropriate configuration to be gripped by a lockbGlt installation gun to pull the pintail 412 through holes in work pieces. While Idifferent configurations may be used, the pull section 422 illustrated defines ¦¦pulling lands 426 and pulling grooves 428 thereon adapted to be gripped by a ¦lockbolt installation gun as will become more apparent., The locking collet 411 as best seen in Figs. 5 and 24, , I includes a seamless annular side wall 43~ concentrically arranged about central "~ , axis Ac with a length LC normally about the same as the length of the su~port ,, I section 424 of pintail 412. The collet 411 has a leading e~nd 431 and a trailing , .
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j end 432. Side wall 430 clefines a cylindrical central passage 434 theret~lrough I
concentric about axis Ac with a diameter dcp which is just sufficient for collet 411 to be slidably received onto the support surface 425 of pintail 412 and support surfa~e 462 of pintail connec-tor 462 and be in bearing support thereon. The side wall 43~ defines a peripheral surface 433 thereon concentric about axis Ac which may have a number of different shapes depending on its final use. For instance, the sur-face 433 may be cylindrical with a diameter Il less than the holes through the work pieces so that collet 411 simply locks ¦I the pintail 412 onto the pintail connector 460 of fastener 410 when the should-O ¦¦ ers 469 and 478 are engaged and collet 411 slipped over this connection. On ¦i the other hand, the surface 433 may be shaped to expand the holes through the I ;
¦ work pieces in addition to locking the pintail onto the pintail connector.
This latter shape is the shape illustrated herein and will be explained in detai1.

I AS seen in Figs. S and 24 the side wall 430 includes a leading pilot section 435 and a trailing expansion section 436. The pilot section 435 defines a cylindrical pilot subsurface 430 of surface 433 on the outside thereof concentric about the collet central axis AC. Pilot subsurface ¦ I
438 has a len~th LpC and a diameter dpC sufficient to locate the collet 411 coaxially with the centerline of the holes through the work pieces when sub-surface 438 extends into the holes.
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Expansion section 436 includes a leading expansion sub-surface 440, an intermediate land subsurface 441, and a trailing contraction ¦
subsurface 442 of surface 433, all concentric about the central axis AG f I collet 411. The expansion subsurface 440 tapers outwardly fro~ the diameter ¦ dPC of pilot section 435 to a trailing major diameter dEM where the major diameter dEM is greater than the initial diameter of the holes through the work pieces by that amount which it is desired to expand holes. The land I! ~ j I

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,, ' . ' ' , ' ` ~' ' . '''` ~ ','` :' ' ,` ' ' 1 ~1D589Z2 subsurface 441 is cylindrical with the major expansion diameter dEM and joins ¦ with the trailing énd of expansion subsurface 44u. The land subsurface 441 ¦ has a convenient length which allows the expansion subsurface 440 to be re-ground. The trailing contraction subsurface 442 joins with the trailing end of the land subsurface 441 and tapers inwardly from the diameter dEM to a smaller diameter dCM. The diameter dCM is at least as small as the root diameter dTR of threads 419 on fastener 410 to prevent damage to threads 419. 1 -The juncture of su~surFaces 440 441 ar~ 442 with each other are smoothly rounded.
. I , O The trailing end of the side wall 430 defines a rear~
wardly facing driven face 450 concentrically located about the collet axis Ac and lying in a plane normal -to axis Ac. The face 450 joins with the contract- ¦
I ion subsurface 442 and is engaged by the leading driving face 420 on fastener 410 to force the collet 411 through the holes through the work pieces.

The collet 411 may be provided with a clearance counter bore at the trailing end of passage 434 to provide a clearance over the junc-tur~ of the pintail connector 460 and the leading end of the engagement I section 415 of fastener 410 and prevent the collet 411 from sticking on the fastener 410 when the assembly is forced through the holes in the work pieces.
~0 A breakneck groove may be formed in the pintail connector 460 at its juncture with the leading end of the engagement section 415 of fastener 410 to facili- ;
tate the removal of the pintail connector 460 after fastener 410 is installed.

For maintaining the fastener 410 coaxial with the pin-tail 412 a V-shaped notch 480 may be provided in shoulder 469 on pintail con- , ;
nector 460 seen in Fig. 14 which opens onto the push edge 462 at its wide end while a mating V-shaped projection 481 may be provided on the support section 424 of pintail 412 as best seen in Fig. 15. As the shoulder 478 on pintail 412 is ins rted lnto recess 465 in pintail connector 460 of fastener 410 the ..~

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projection 481 on pintail 412 will fit into no-tch 480 on fastener 410 to positively coaxially align the fastener 410 with pintail 412 even if no collet I 411 is used. When the pintail 412 is pulled, any loose motion between the ¦l fastener and pintail will be compensated for as the projection 481 on pintail I .
: ¦l 412 is forced into the notch 480 in fastener 410 to maintain the fastener 410 and pintail 412 coaxial.
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5~3~22 I INSTALLATION TOOLING
l l I All of the embodiments of the fastener F, collet sup-¦i port 59 and collet C are installed in the same general way. That is, the col-¦ let C is maintained coaxial with the leading end of the fastener F by the ¦ collet support S and the collet C is forced through the holes H in the w~rk pieces P immediately preceeding the fastener F to first expand the holes and then rnove the fastener F into place in the holes. The collet C is then re- ¦
moved and the collet support S may subsequently be removed to complete the joint. It will be seen that the collet C and fastener F can be forced into the holes in the work pieces by either pushing on the fastener, pulling on the collet support S, or a combination of both.

One arrangement for exerting a pushing force on fas- I ~
! tener F and/or a pulling force on the collet support S is illustrated in Fig. ! ~ :
¦ 21 and designated generally TA. The arrangement TA includes a conventional ¦
¦l lockbolt installation gun LG which carries nose assembly N and a conventional ¦
¦I rivet gun RG which carries driving member DM. The lockbolt gun has an activat-¦
ing trigger TL and the rivet gun RG has an activating trigger TR. The lock-bo~t gun LG is connected to a conventional flu;d pressure source PS through an ¦adjustable regulator valve RV and the rivet gun RG is connected to the fluid ¦ ~pressure source PS through a cut-off valve CV with an operating mechanism OM. 1 ;1 The cutoff valve CV serves to disable the rivet gun RG until the lockbolt gun LG is activated to prevent the work pieces from carrying the full load of the rivet gun. The operating mechanism OM is appropriately connected to the ¦
lockbolt gun LG so that valve CV supplies fluid under pressure to the rivet gun RG when the lockbolt gun is activated. One such connection is illustrated li as a switch SW electrically connected to mechanism OM as a solenoid. It will ¦l also be understood that the lockbolt gun LG or the rivet gu,n RG may be used ¦-separately in conventional manner.

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Il WhL~n the Fastener F is threa~ed an(l provided with a~¦ positive connection to the collet support S as illustrated in Figs. 1, 3 and 5 the collet C Can be removed and the support S used to assist in installing a nut on the threads of the fastener. When it is desired to axially tensile pre-load the fastener F while the nut is tightened, a preload adapter 500 seen in Figs. 19 and 20 may be used in combination with a conventional lockbolt in- ,stallation gun having a hose assembly N to space the nose assembly sufficiently¦away from the work pieces to allow the nut to be tightened.

I The preload adapter 500 includes generally a main body O 501 with a centerline CLpA. The main body 501 includes an end bearing wall 502 oriented generally perpendicular to the centerline CLpA and an annular guide wall 504 integral with and extending outwardly from one side of the bearing wall 502 concentrically about the centerline CLpA. Thus, it will be `
seen that a guide chamber 505 is defined by wall 504 an~ wall 502 with a diameter dN which is sufficient to just receive the nose assembly N of the lockbolt pulling gun therein so that the workin9 face WF of the nose assembly ¦
N bears against the bearing surFace 506 in chamber 505 and the support S
passes through a central passage 508 therethrough concentrically arran~ed ¦ ;~
about the centerline CLpA. At least a pa;r of internally threaded holes 509 are defined in the bearing wall 502 on diametrically opposite edges of the opposed face of the bearing wall 502 and shoulder bolts 510 are provided to ~ be screwed into the passages 509 to space the bearing wall 502 a prescribed ¦ distance from the work pieces P. The shoulder bolts 510 may be acquired in -~
¦ different lengths so that the distance that the bearing wall 502 is spaced ; I from the work pieces P can be varied. ~ ~

l While a conventional wrench may be used with the I i ¦ adapter 500, a modified wrench WR is shown in Figs. 19 and 20 which is capti- ¦
vated ont the adapter 500 and forms a part thereof. The wrench WR has a nut ,' 11' . I ';
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'2 driving element DE which is rotatably mounted on the driving handle DH so that the driving element DE can ratchet in one direction and drive in the other as the handle DH is rotated. It will be seen that the oFfside of the driving ele-ment DE defines an annular retaining recess and an annular retaining flange is provided on the bearing wa11 502 which captivates wrench WR so that the driving element DE is freely rotatable with respect to the body 5nl yet the drlving element axis is maintained coaxially with the centerline CLpA. It will thus be seen that the shoulder bolts 510 also serve to locate the wrench WR with respect to the fastener F.
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, ~ith the wrench WR engaging nut NT the nose assembly N is then reinserted back over the support S until its workin~ face WF bears against the bearing surface 506 on bearing wall 502. The working pressure to the lockbolt installation gun is adjusted in known manner to exert a pre-scribed minimum preload force on the fastener F through the support S and nose Iassembly N. One way to set the minimum preload force is using a conventional force gauge especially adapted for use with lockbolt installation guns. The , ¦
installation gun is activated to preload the fastener F and the wrench WR used , to tighten the nut NT while this preload is maintained. The nut NT thus locks the preload into the fastener F to assure the desired preload on the joint.
After the nut NT is tightened to lock the preload in the joint, the nose assem bly N and adapter 500 are removed. The support S can then be removed to fin- I
ish the joint. I

The pintail 412 used with fastener 410 and the preload adapter above may be incorporated in the tool used to install fastener 410 as best seen in Fig. 29. The tool IT includes a tubular body TB partly shown in ' the figure which reciprocally mounts a driving member DP therein for reciprocal movement along the centerline CL-T of the tool. The pintail 412 is affixed to driving member DP for movement therewith. The body TB has an operating end OE
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adapted to engage the work pieces P about the holes H. A ratchet wrench WR
may be captivated in the tubular body TB adjacent the operating end OE o~ the tool to install a nut NT on the fastener ~10. The wrench I~R has a nut driving ~
element DE which is rotata~ly mounted on the driving handle DH and provided witha ratchet mechanism so that the driving element DE can ratchet in and direction and drive in the other as the handle DH is rotated. It will be seen that the off side of the driving element DE defines an annular retaining recess RR on one of its ends projecting beyoncl the handle DH. The retaining recess RK is concentric about the axis of the driving element DE which coincides with the tool axis CL-T.

The tubular body TB has an annular bearing wall lBW ¦
adjacent its operating end defining a generally cylindrical wrenching chamber lBC therein concentric about centerline CL-T and opening ~nto the operating end OE of tool IT. The chamber TRC has a diameter such that the handle DH
and driving element DE can be rotated therein. A cutout TBT is providéd through wall TBW so that the handle DH can project radially therethrough and is sufficiently wide to permit the wrench WR to be operated. The end of wall ¦ ;
TBW may be provided with an annular inwardly turned llp TBL to bear against ¦the work pieces P about holes H.

The wrench WR is maintained in tool IT by an annular flange TBF on the inside of body TB which projects into the recess RR on the driving element DE of wrench WR to provide a loose fit therebetween so that l 1 the driving element DE is freely rotatable with respect to body TB. The drivin~element DE is provided with internal wrenching surfaces WS which mate with the external wrenching surfaces on nut NT to drive the nut. It will be noted that the wrenching surfaces WS have a length about twice the thickness of the ; ;
nut NT as will become more apparent.
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The driving member DP is driven by conventional !neans such as a hydraulic or pneumatic pressure mechanism HPM seen in Fig. 29. The pintail 412 is oriented so that the support section 424 thereof can be select-ively extended out of operating end OE of the tool IT. This allows the p;n-tail 412 to be selectively extended through the holes H in work pieces P so that the fastener 410 can be hooked thereonto for installation. The driving ¦ -~
member DP may be constantly urged away from the operating end OE of the instal-~ -lation tool IT with a small amount of force so that the tool IT will maintain tension in the connection between the fastener 410 and the pintail 412 as shown by spring SDM in Fig. ~9.
. I '~
In the installation of a fastener 410 using the tool IT without collet 411, nut NT is inserted into the driving element DE of the I ~1 wrench WR over the pintail 412. The tool IT is triggered by trigger T-E to I :
extend the support section 424 on the pintail 412 from the operating end of ¦ ~:
the installation tool IT. The support section 424 of the pintail 412 is in- I
serted through the holes in the work pieces P from the off side OS thereof so I :
that the support section 424 on the pintail 412 proiects out of the near side ¦NS of the work pieces P opposite the installation tool IT. The fastener 410 is now hooked onto the support section 424 so that the V-shaped projection Q81 on the pintail 412 mates with the V-shaped notch 480 on the fastener 410. 1 .
The mating of projection 481 with notch 480 serves to maintain the fastener 410 coaxial with the pintail 412. The pintail 412 also serves as a pilot to keep the fastener 410 generally centered within the holes ~l. When the trigger T-F on tool IT is released, the driving member DP is urged away from the operating end OE of the tool so that the previously mentioned small force is applied to the pintail 412 as shown by spring SDM. This small force pulls the ¦
fastener toward the holes H. If the holes H are of such a diameter so that :
there wil e an interference Fit, the diameter of the h~les will be smaller '.'. , , ':
-:~ . I ' .
"'' :

- 3 7 .:
, . .

~L~5~Z2 , i I than the diallleter of the bearing section of the -fastener 410 and larger ~han the cr~st diameter of the threads 419. In that case, the fastener 410 will be pulled into the holes until that end of the holes H at the near side rlS
will engage the transition surface 418.

When the tool IT is activated through trigger T-R to : apply the main pulling force, the driving member DP will be forced away from I :
¦ the operating end OE of the tool IT with sufficient force to pull the bearing ¦ section 414 of the fastener 410 into the holes H with the pintail 412 passing through the nut NT. When the head 416 of the fastener 410 bottoms against -~
~LO the near side NS of the work pieces P as seen in Fig. 29, i t will be seen ~:
that the leading end of the engagement section 415 now just entered the nut NT.
I An annular spring washer Ws may be provided in the driving element DE at its ¦
inboard end to.resiliently urge the nut NT against threads 419 so that the nut NT can be started onto the threads 419. When the nut NT is rotated by the driving element DE, the nut will be screwed onto the threads 419. While the tool IT maintains an axial tension load on the fastener 410 through the pintail 412, the wrench WR is operated so that the driving element DE threads : the nut NT onto the threads 419 and tightens the nu-t about the fastener 410 to lock it into position. At this time, the major pulling force on the driv~
:~0 ing member DP is relaxed so that the support section 424 on the pintail 412 1 :
can be unhooked from the pintail connector 460 on the fastener 410 and the tool IT removed along with the pintail 412. The pintail connector 460 may be I ............ -broken from the fastener 410 i-f the joint formed is a weight critical joint.
Another nut NT can then be inserted into the driving element DE and the cycle repeated to install other fasteners 410.

Il . . I :' ' Il -:' Il . . ,.
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,1 OPERATIO~I
1l~

Because the embodiments of the invention are used I similarly, the operation of only the first embodiment will be described in ¦ detailg it being understood that the other embodiments will be installed similarl~
Referring to Figs. 16-18, the installation of the first embodiment of the in- ¦vention is illustrated.

~; There is a definite relationship between the diarneter dB of the bearing section 14 of the fastener 10, the diameter dEM of the ex-pansion section 36 and the diameter dpC f the pilot section 35 of the collet I11, the initial hole diameter ~HI and therecoVered hole diameter DHR of the holes¦
H after passa9e of the collet 11 therethrough, and the final interference hole diameter DHF when the fastener is installed in the holes. Usually, the diam-eter dB of the bearing section of the ~astener 10 is the controlling diameter since it is desirable to use a standard size fastener. Thus, if it is desir- ¦¦ able to place the bearing section 1~ of the fastener 10 into an interference fit of a prescribed amount such as .003 inch, then the recovered hole diameter ¦DHR must be .003 inch less than the diameter dB of the bearing section of the fastener. When the material of the work pieces P is known, the recovered hole ¦diameter DHR can be predicted and this determines the major diameter dEM of the expansion section 36 of the collet 11. The diameter dEM can be calculated to be that amount larger than the recovered hole diameter DHR to make the I recovered hole diameter DHR the desired amount smaller than the diameter dB
of the bearing section of the fastener 10. Once the diameter dEM is deter- `
mined, the initial hole diameter DHI can be determined and is that amount less than the maximum expansion of the holes as determined by the diameter dEM by which it is desired to expand the holes. Usually, the amount the holes H are `
to be expanded is set by available coldworking data. Once,the initial hole diameter DHI is determined, this determines the diameter dpC cf the pilot ,1 ' I

I ,.. .
~ - 39 -., . , ~, ~ ' z ¦, section 35 of the collet 11. The diameter dTC of the engagement section 14 of ~
the fastener 10 is usually standard but is less than the recovered hole diame- j -ter DHR to prevent -the engagement section 14 from scratching the inside of the holes H as it passes therethrough. For instance, if a 5/16 inch fastener is 1I to be installed and it is desirable that the fastener bearing diameter dB of ¦1 .311 inch is to be in interference of .003 inch through 7075-T6 aluminu~!, then I ;
the diameter dEM should be .315 inch to produce a recovered hole diameter ,I DHR f .308 inch where the initial hole diameter is .300 inch. Thus, the , ;
diameter dpC of the pilot section 35 should be just slightly less than the initial hole diameter DHI or .299 inch. For the standard si~e 5/16 inch fastener, the engagement diameter dTC would be .304 inch which is sufficiently I I
less than the recovered hole diameter D~IR to allow the engagement section 14 to pass through the recovered holes H without scratching same.

; ¦ Referring to Fig. 16, it will be seen that the collet ¦11 is assembled onto the pintail 12 until the passage 34 in the collet 11 is ¦!in bearing contaot with the support surface 25 on the support section 24.
The driven face 50 on collet 11 is also bearing against the driving face 20 ~
I~on the end of the engagement section 15. The leading end of the pintail 12 - '!' I Ilis inserted through the holes H and the pulling section 22 is gripped by the ~ ¦Inose assembly N of a conventional lockbolt installation gun. When the holes H
; ~'are tobesignificantly expanded, a backup washer BW may be positioned between the nose assembly N and the off side OS of the work pieces P as illustrated I~in Figs. 16 and 17 to prevent a lip from being extruded about the holes on the ;
Iloffside of the work pieces. The backup washer BW may have a protective coat-ling PC such as plastic or paint on its face bearing on work pieces P.

When the installation gun is activated, the nose assem- i ibly N pulls the pintail 12 and thus fastener 10 toward the nose assembly N
thereby forcing the collet 11 through the holes H to expand same as seen in Fig. 17. The driving member DM of the rivet gun RG may also be used to 1, ' 'i .

, : :
' ~' , ~s~ z Il simultaneously exert a pushing force through the head 16 of fastener ln. As ¦I the collet 11 passes through washer BW it also expands the hole through the ¦ washer. It will be noted that the major diameter dTC of the engagement ~¦ section 15 is less than the recovered diameter DHR of the holes H through thework pieces so that the engagement section 15 passes centrally through the holes H after expansion and recovery without contacting the side of the holes.
It will further be seen in Fig. 17 that the bearing section 14 of the fastener 10 is pulled into the holes behind the collet 11. If an interference fit is desired, it will be seen that the diameter dB of the bearing section 14 is O larger than the final diameter DHF of the holes H by the amount of interter- ¦
I ence desired. In an interference installation, the lead-in surface 18 serves ¦ ~
¦ to re-expand the holes H from the recovered diameter DHR 50 that the bearing ~ -section 14 can pass into interference with the holes. As the nose assembly N
continues to pull the pintail 12 toward the nose assembly N, the collet 11 passes thuough the holes H, the backup washer and into the nose assembly N. I `
The bearing section 14 is also pulled into the holes H until the head 1 bears against the opposite side of the work pieces from the nose assembly N
as seen in Fig. 18.
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The working pressure on the lockbolt installation gun 0 may be set such that the pintail 12 will fracture at the breakneck section 21 or if the working pressure is lowered, the support section 24 and pulling section 22 may be left intact on fastener 10 when a self-releasing nose assembly is used. If the pintail 12 is left intact on the fastener 10, it can be used to facilitate the installation of the nut NT onto the engagement section 15 as seen in Fig. 20 as described above. I
I ' .
When the second embodiment of the invention is being installed, it will be noted that the trailing diameter dCM of the collet 111 is at least as large as the leading diameter dBL of the bearing section 114 .

- 41 - i ,, ~ , . ........ .

1 ~s89~2 Il i i so that the leading end o-f the bearing sec-tion 114 can pass into the holes without damaging the hole surfaces. As the holes recover, they are prevented from fully recovering by the bearing section 114 immediately following the collet 111 to form the interference f;t. Afterthe collet 111 has been moved completely through the holes H as seen in Fig. 22, it will be seen that the ¦hole has a final size and shape corresponding to the size and shape of the bearing section 114 of fastener 110. Because the bearing section 114 prevents ¦
the holes from fully recovering, it will be seen that the bearing section 114 is in interference fit with the holes H. If the nose assembly N is of the ¦
LO self-releasing type, the nose assembly can be removed from the pintail 1~2 and then the collet 11 slidably removed therefrom as illustrated having been done in Fig. 22. The pintail 112 is removed by exerting a lateral rather than axial force thereon to fracture breakneck section 121 to prevent the loss of preload on the`final joint. ¦ `

Experimental data has shown that the force required ¦ `-to moYe an expansion type tapering surface through holes is generally inversely~
; proportional to the slope when the slope is small. Because the average slope . l ~
of the expansion s~rface 140 on the collet 111 is much greater than the slope o~the reverse taper subsurface 115R on the bearing section 114 of the fastener 110, it will be seen that the force required to remove the fastener 110 from the holes by movement toward the head is significantly greater than the force required to force the fastener 110 into the holes. Thus, the forces of the work pieces P on the fastener 110 will always try to maintain the fastener 110 in the holes. It will be further seen that if the tension load on the joint is low such as in a shear application, the need for a locking device such as a nut or swagable collar is eliminated. The forward taper subsurface 115F maintains the work pieces P clamped together. The shape of bearing section 114 may be used on any embodiment of the fastener., l''' .
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¦¦ When the third embodiment of the invention is installedl ¦ as seen in Fig. 23, each of the flights 2302-2304 on the coil member 211 in- ¦
¦ crementally expand the holes -from the diameter of -the adjacent lea~ing flight to the outside diameter o-f the particular flight. The total expansion, howeYer is determined by the difference between the initial hole diameter DHI and the outside diameter dEM of the trailing flight 2304.

Any of a number of different lubricants may be used to coat the expansion~ land and contraction surfaces of the collets shown herein.
One lubricant which may be used is an electroplated film such as cadmium. This ~O film flows under coldworking pressure to act as a lubricant and may be re-plenished by replating these surfaces. Also, a wax may be used as the lubri-¦ cant. Various dry film lubricants may also be used such as the layer lattice compounds of molybdenum disulfide (MoS2), tungsten disulfide (WS2), graphite, and graphite floride (CFX); the plastic polyimide polymers; or the calcium floride based coatings. Cetyl alcohol may also be used as a lubricant.

The material used to make the expansion sections of the collets may also be self-lubricating. Alloy steels which contain free graphitel ~
are such materials. These alloy steels usually contain a relatively high ¦ -carbon content, normally 1.4-1.5%, and silicon, normally .5-1.5% to promote ¦
>o the formation of microscopically fine particles of the free graphite. Other alloying elements such as manganese and molybdenum may be used to stabili~e the formation of the free graphite. Such steels have the necessary hardness and strength to withstand the forces required for hole expansion. One such !
steel alloy which has been found satisfactory typically contains 1.45% carbon, 1.25% silicon, 1% maximum manganese and .25% maximum molybdenum.
. . 1..

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,.
CLEANING APPARATUS

Rather than providing a lubricant on the collets, it is to be understood that the inside of the holes H may be lubricated usiny any of the aforementioned lubricants. Figs. 25 and 26 illustrate a cleaning appli-cator attachment which may be used in conjunction with the invention disclosed herein or with a standard fastener to apply a liquid lubricant and/or sealant to the inside of the holes H immediately prior to installation of a fastener therein and as an incident thereof.

The illustrated embodiment of the cleaning applicator is designated generally by the numeral 600. The cleaning applicator 600 serves to clean the holes and apply a lubricant and/or sealant to the hole surfaces. Cleaning applicator 600 includes a main body 601 with a generally ~ -~
circular end wall 602 and an annular side wall 604 integral with the trailing outside edge of the end wall 602. The wall 604 is concentr;cally located about the centerline CLcA of the cleaning applicator 600. A cavity 605 is defined within the side wall 604 which receives the leading end of the collet support or fastener therein as seen on pintail 12 in Fig. 26. The cavity fiO5 has a diameter dCV which is less than the major diameter dpS of the puliing section so that when the leading end of the pulling section is inserted into ~he cavity 605, the pulling section 22 is resiliently engaged by the inside edge of the side wall 604 to hold the cleaning applicator 600 in position.
It will be noted that the body 601 has an outside diameter dCA which is larger than the initial hole diameter dHI through the work pieces. It will also be ~;
noted that the body 601 may be made out of a soft absorbent resilient material so that the body 601 will be compressed as it is forced through the holes in ~ I
the work pieces as the pulling section is inserted therethrough. Thus, the ~-cleaning applicator 600 serves to remove any burrs from the,holes through the work pieces and a lubricant and/or sealant may be impregnated in the body 601 sg that it is squeezed onto the hole surfaces as the applicator 600 is forced ~'', ' , ~ .' , ' ... . .
" , . . .

~5139Z2 throu~h tl~e work pieces to COdt them with the lubricant and/or sealant. It is further to be understood that the body 601 nlay be made out of a plastic encap-sulating material with the lubricant and/or sealant encapsulated therein so that when the body 601 is compressed as it is Forced throuyh the holes the en-capsulation will be broken and the lubricant and/or sealant ~ill be dispersed j onto the inside of the holes to coat them. The lubricant and/or sealant is ¦ usually a liquid.

Any number of different configurations may be used for the applicator 600. The dpplicator 6no should be removably connected to the leadiny end of the fastener or collet support 50 that it can be removed ~ ~ before in alletion is completed.

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11 ' i ~ .
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1, 1

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A fastener assembly for connecting together work pieces with aligned holes therethrough of an initial diameter comprising:
a fastener with a fastener central axis, a leading end and a trailing end including an elongate bearing section and an enlarged head section integral with the trailing end of the bearing section, said fastener defining a forwardly facing driving face thereon generally normal to the fastener central axis and leading the bearing section;
a separate expansion collet with an expansion central axis, a leading end and a trailing end and defining a collet central passage therethrough concentric about said expansion central axis; an outside expansion surface thereon concentric about the expansion central axis that enlarges outwardly from a minor expansion diameter smaller than the initial hole diameter at the leading end of the expansion surface to a major expansion diameter larger than the initial hole diameter trailing the minor expansion diameter; and a rearwardly facing driven face thereon generally normal to the expansion central axis to be engaged by the driving face on said fastener to force said expansion collet through the holes; and an alignment member including a support section positively connected to the leading end of said fastener and a pulling section leading said support section and adapted to be engaged to pull said fastener assembly into the holes, said support section adapted to removably fit in said collet central passage to removably support said collet in operative association with said fastener so that the expansion central axis of said expansion collet is coaxial with the fastener central axis with the driving face on said fastener engaging the driven face on said expansion collet to force said expansion collet through the holes ahead of said fastener to expand the holes as said fastener is moved into the holes.

2. The fastener assembly of claim 1 wherein said expansion collet further defines a pilot surface thereon concentric about the expansion central axis and leading said expansion surface, said pilot surface having a prescribed pilot diameter along its length substantially equal to the initial hole diameter so that said pilot surface maintains said expansion collet and said fastener coaxial with the holes in the work pieces as the fastener assembly is forced into the holes with said pilot surface leading.

3. The fastener assembly of claim 1 wherein said expansion surface on said expansion collet is convex with a decreasing slope from its leading end toward its trailing end of increasing mechanical advantage.

4. The fastener assembly of claim 1 wherein said fastener further includes an engagement section thereon leading said bearing section and concentric about said fastener central axis, said engagement section adapted to be engaged to lock said fastener in place and defining said driving face on the leading end thereof.

5. The fastener assembly of claim 4 wherein said engagement section of said fastener defines nut receiving threads thereon.

6. The fastener assembly of claim 5 wherein said driven face on said expansion collet has an outside diameter at least as small as the root diameter of said nut receiving threads on said engagement section of said fastener, said expansion collet further defining a clearance surface thereon extending outwardly from and forwardly of said driven face to prevent damage to said nut receiving threads on said engagement section of said fastener as said expansion collet is forced through the holes.

7. The fastener assembly of claim 1 further including pulling means adapted to bear against the work pieces and engage said pulling section to pull said fastener assembly into the holes.

8. The fastener assembly of claim 7 further including drive means for exerting a pushing force on said fastener to push said fastener assembly into the holes.

9. The fastener assembly of claim 8 further including control means for enabling said drive means only when said pulling means is exerting a pulling force on said fastener assembly.

10. The fastener assembly of claim 1 wherein said bearing section on said fastener defines a reverse taper bearing surface thereon having a leading major bearing diameter adjacent the leading end of said bearing section and tapering inwardly along said bearing section to a trailing minor bearing diameter smaller than said leading major bearing diameter.

11. The fastener assembly of claim 1 wherein said major expansion diameter on said expansion collet is sufficiently larger than the initial hole diameter to cause said expansion collet to non-elastically expand the work pieces about the holes as said expansion collet is forced therethrough to coldwork the holes.

12. The fastener assembly of Claim 10 wherein said bearing section on said fastener defines said driving face on the leading end thereof, wherein said major bearing diameter is located at said driving face;
and wherein said expansion collet has a trailing outside diameter at said driven face thereon at least as large as said leading major diameter on said bearing section of said fastener.

13. The fastener assembly of Claim 10 wherein said trailing minor bearing diameter trails said leading major bearing diameter by a prescribed distance less than the length of said bearing section and wherein said bearing section further defines a trailing forward taper bearing surface extending between said leading reverse taper bearing surface and the trailing end of said bearing section, said trailing forward taper bearing surface tapering outwardly from said trailing minor bearing diameter to a further pre-scribed trailing secondary major bearing diameter adjacent the trailing end of said bearing section, said trailing secondary major bearing diameter larger than said trailing minor bearing diameter.

14. The fastener assembly of Claim 11 wherein said bearing section on said fastener defines a leading reverse taper bearing sur-face thereon having a leading major bearing diameter at the leading end of said bearing section and tapering uniformly inwardly along said bearing section to a trailing minor bearing diameter smaller than said leading major bearing diameter, said trailing minor bearing diameter trailing said leading major bearing diameter by a prescribed distance less than the length of said bearing section; said bearing section further defining a trailing forward taper bearing surface extending between said leading reverse taper bearing surface and the trailing end of said bearing section, said trailing forward taper bearing surface tapering outwardly from said trailing minor bearing diameter to a further prescribed trailing secondary major bearing diameter adjacent the trailing end of said bearing section, said trailing secondary major bearing diameter larger than said trailing minor bearing diameter; said bearing section defining said driving face on the leading end thereof at said major bearing diameter;
and wherein said expansion collet has a trailing outside diameter at said driven face thereon at least as large as said leading major diameter on said bearing section of said fastener, said leading and trailing bearing diameters smaller than said major expansion diameter of said expansion collet and larger than the normal unrestrained recovered hole diameter in the work pieces after expansion to cause the work pieces to grip the bearing section of said fastener upon installation.

15. The fastener assembly of Claim 1 wherein said expansion collet is a helically wound coil member including a plurality of interconnected resilient helical flights; and wherein said support section on said alignment member engages and supports said coil member about the expansion central axis so that at least the leading of said helical flights has a first effective outside diameter at least as small as the initial hole diameter, at least one of the intermediate of said helical flights trailing the said leading helical flight has a second effective outside diameter larger than said first outside diameter, and at least one of said helical flights trailing said helical flight with said second outside diameter has said major expansion diameter as its effective outside diameter so that when said coil member is axially forced through the holes, leading end first, while supported on said support member, said flights on said coil member will expand the holes from the initial diameter along the length of the holes through the second effective diameter and finally to said major expansion diameter.

16. The mandrel assembly of Claim 15 wherein said helical flights of said coil member have a circular cross-sectional shape.

17. The fastener assembly of Claim 1 wherein said expansion collet is a seamless annular locking collet defining a collet central passage therethrough concentric about said expansion central axis; and wherein said alignment means includes a pintail connector integral with the leading end of said fastener, a pintail coaxially aligned with said fastener, and connection means for removably connecting said pintail to said pintail connector, said locking collet slidably received over said pintail connector and said connection means on said pintail to positively yet removably connect said pintail to said pintail connector.

18. The fastener assembly of Claim 17 wherein said pintail connector defines an arcuate support surface thereon concentric about the fastener central axis, said pintail connector including a push shoulder thereon at the leading end thereof and defining a connector recess therein trailing said shoulder, said forwardly facing driving face arranged about the trailing end of said pintail connector; and, wherein said pintail includes a support section at the trailing end thereof defining a generally cylindrical support surface thereon concentric about the central axis of the pintail, said support section further including a pull shoulder at the trailing end thereof removably received in said connector recess behind said push shoulder on said pintail connector to force said fastener into the holes through the work pieces as said pintail is pulled through the holes, said arcuate support surface on said pintail connector forming a continuation of said cylindrical support surface on said pintail, said expansion collet engaging said arcuate surface on said pintail connector and said cylindrical support surface of said cylindrical support section of said pintail to positively yet removably lock said pintail onto said fastener with said locking collet coaxial therewith.

19. The fastener assembly of Claim 1 further including pulling means adapted to bear against the work pieces and engage said pulling section on said alignment member; an internally threaded nut; and a preload adapter including a body defining a bearing face thereon adapted to be engaged by said pulling means and an opening therein slidably receiving said pulling section of said alignment member therethrough for engagement by said pulling means while bearing against said bearing face, and spacing means operatively connected to said body adapted to engage one of the work pieces about the holes, said spacing means adapted to space said body a prescribed distance from said work piece so that said pulling means is supported by said bearing face while said pulling means engages said pulling section to pull said fastener and the work pieces together by exerting a force in a first direction on the work pieces through said spacing means while exerting a force in the opposite direction on said fastener to allow said nut to be screwed onto said threaded engagement section.

20. The fastener assembly of Claim 19 wherein said preload adapter further includes wrenching means for selectively and drivingly engaging said nut to screw said nut onto said fastener.

21. The fastener assembly of Claim 20 wherein said preload adapter further includes captivating means for limiting movement of said wrenching means toward and away from said bearing surface while allowing relative rotational movement between said wrenching means and said body.

22. The fastener assembly of Claim 21 wherein said spacing means on said preload adapter is adjustable.

23. The fastener assembly of Claim 1 further including a cleaning device comprising a compressible body having a first diameter larger than the initial hole diameter removably mounted on the leading end of said pulling section of said alignment member to clean the holes as said pulling section forces said compressible body through the holes, and a liquid carried by said compressible body, said compressible body expelling said liquid onto the hole surface as said cleaning device is forced through the holes.

24. A method of installing the fastener assembly of Claim 1 comprising the steps of simultaneously exerting a pulling force on said fastener and a pushing force on said fastener to force said fastener into the holes.

25. A method of installing the fastener assembly of Claim 1 comprising the steps of simultaneously exerting a pulling force on said expansion member and a pushing force on said fastener to force said fastener into the holes.

26. A method of forming a fastener joint comprising the steps of: inserting an expansion member in the holes through the work pieces where the expansion member has an expansion section with a major diameter larger than the initial diameter of the holes and a fastener to be installed in the holes is coaxially aligned with the expansion member so that the leading end of the fastener is at the trailing end of the expansion member exerting a pushing force on the fastener; and, simultan-eously exerting a pulling force on the expansion member to force the expansion member through the holes and the fastener into the holes with the expansion member immediately preceeding the fastener through the holes.

27. A fastener assembly for connecting together work pieces with aligned holes therethrough of an initial (claim 27 cont'd) diameter comprising:
a fastener with a fastener central axis, a leading end and a trailing end including an elongate bearing section and an enlarged head section integral with the trailing end of the bearing section; said fastener defining a forwardly facing driving face thereon generally normal to the fastener central axis and leading the bearing section, and a locating passage therein centrally located with respect to and opening onto the leading end of the fastener;
a separate expansion member with an expansion central axis, a leading and a trailing end removably and operatively associated with the fastener, and including an expansion section and a pulling section leading said expansion section and adapted to be engaged to pull said expansion member into the holes; said expansion section defining an outside expansion surface thereon concentric about the expansion central axis that enlarges outwardly from a minor expansion diameter at the leading end of the expansion surface to a major expansion diameter larger than the initial hole diameter trailing the minor expansion diameter, and defining a rearwardly facing driven face thereon generally normal to the expansion central axis to be engaged by the driving face on the fastener to force the expansion member into the holes; and alignment means for maintaining the fastener and expansion member coaxial as the fastener and expansion member are forced through the holes with the expansion member leading the fastener to expand the holes and the driving face contracting the driven face, said alignment means including a locating projection positively connected to the trailing end of said expansion member concentric with said expansion central axis and having a size and shape such that said locating projection is just slidably received in said passage in the leading end of said fastener to maintain the leading end of said fastener concentric with said expansion central axis and coaxial with said expansion member.

28. The fastener assembly of Claim 27 further including pulling means adapted to bear against the work pieces and engage said pulling section to pull said expansion member through the holes; drive means for exerting a pushing force on said fastener to push said fastener assembly into the holes; and control means for enabling said drive means only when said pulling means is exerting a pulling force on said expansion member.