CA1101244A - Spherical multi-blade tool - Google Patents

Abstract

SPHERICAL MULTI-BLADE TOOL
Abstract of the Disclosure The essence of the invention consists in that the blades are inclined relative to the meridian planes of a spherical head mounted on a journal for rotation relative to the geomet-ric axis of this journal, the axis extending at an acute angle to the axis of the tool shank.

Description

The present invention relates to tools for machining bores and holes, and, more particularly, it relates to spheri-cal multi-blade tools.
The invention can be utilized to utmost effectiveness at machining of relatively deep holes twherein the ~epth ex-ceeds the diameter at least tenfold), as well as at machining of holes to a high (i.e., second or third) accuracy class.
Furthermore, the invention can be utilized for machining holes having faceted walls.
In most cases the herein disclosed spherical multi-blade tool is used as a spherical reamer for finishing bores and holes.
The present level of engineering more often than not puts strict requirements before the accuracy of finishing of holes (as high as second and third accuracy classes) and before the roughness of the finished surface, which is not expected to exceed Ra = 0.16 to 1.25 microns. ~le machining of such holes by cutting is usually performed with either cutter tool blocks, or else with floating plates with two oppositely arranged blades. Such tools offer a cutting depth not in excess of 0.1 ... 0.2 mm and the surface finish with the roughness ~a in excess of 1.25 microns, whereby subsequent machining of the holes either by plastic deformation or by grinding is required.
When relatively deep bores or holes are machined, the aforesaid hitherto known tools would not ensure the required accuracy, on account of their relatively rapid dimension-wise wear. To

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attain the required ratings, there have been recently made attempts of using rotary tools with circular blades of ~arious designs. Thus, there is known a design of a disc-type rotary cutter of which the cutting disc has a diameter equalling the diameter of the hole being machined. The axis of the rotation of the disc is inclined relative to the axis of the hole being machined at an angle ~= 15...20, so that the circular blade thereof engages the surfaces being machined by two diametra~ly opposing areas of which one performs cutting, and the other one performs levelling down or rubbing down of the machined surface. The dimension-wise stability of this tool has been enhanced in comparison with the aforementioned traditional ones, however, difficulties encountered at center-ing such a tool in a hole have been found to affect the machin-ing accuracy. This disadvantage accompanied by the unsolved problem of chipping of the shavings has practically prohibited the use of such tools for industrial purposes.
There are also known rotary counterboring blocks or units wherein rotary circular cutters extend at acute and obtuse angles with respec-t to the axis of a hole being machined.
However, tools of this type are bulky and are practically suitable for machining relatively large holes, e.g., those with diameters in excess of 200 mm.
Nowadays, attempts are made in the practice of finishing of holes and bores, aimed at using spherical multi-blade tools for the purpose.
There are already known spherical multi-blade tools -:: - : . ,. . i - . . , . ~ . , , with a head made in the form of a block or unit having two cutting blades arranged on the spherical surface in a meridian section thereo~. ~owever, on account of relatively rapid dimension-wise wear of the blades, these blocks are apt to ~
lose their accuracy of machining. To enhance the dimension- ~ -wise stability, the improved versions of such tools have blades fixed on segments rotatable by an independent drive in a direction opposite to that of the axial feed of the tool. However, even in this case, the dimension-wise stability of the tool is enhanced inadequately. Furthermore, the last-described tool has a complicated structure and cannot have more than two blades, which affects the productivity of the machining operation.
There is known a spherical multi-blade tool for machining bores and holes, wherein the blade-carrying spherical head is mounted on the journal of a holder or shank. The blades extend along the meridian planes of the spherical head, while the spherical head itself is rigidly fixed on the journal which is coaxial with the holder or shank.
In the process of a machining operation, this spherical head effects cutting with the vary same relatively small areas of the blades without their replacement, since the head cannot be rotated on the journal. Consequently, but portions of the blades of the spherical head are used, which portions are subjected to excessive heating and rapid wear.
This involves an untimely failure of the tool as a whole, to say nothing of the affected productivity and machining accuracy.

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It is the main object of the present invention to provide a spherical multi-blade tool for machining bores and holes, which should offer high stability.
It is another object of the present invention to provide a spherical multi-blade tool for machining bores and holes, which should have a wide field of uses.
It is still another object of the present invention to provide the tool of the type referred to, which should provide for a high efficiency of the machining operation.
It is yet another object of the present invention to provide a tool of the type referred to, which should enable to improve the quality of the holes or bores machined there-with.
With these and other objects in view, the essence of the present invention resides in a s~pherical multi-blade tool wherein the spherical head carrying the blades is mounted on the ~ournal of a shank, in which tool, in accordance with the present invention, the said blades are inclined to the meridian plane of said spherical head, the latter being mounted on said journal for rotation about the geometric axis of said journal, the last-mentioned axis extending at an acute angle to the axis of said shank.
Owing to the provisions for the rotation o~ the spherical head on the journal which has its geometric axis extending at an acute angle ~ to the axis of the holder or shank, there takes place continuous automatic replacement of the working areas of the blades of the spherical head with .: . , : . :. : . .,. - . . -t~2~L4 respect to the hole or bore being machined, with an oscillatory motion of these portions within a spherical band defined by a central angle equalling 2G~. This means that the stability of the tool, as compared with the prior art, is increased at least as many times as there are such working portions accommo-dable along each blade within said spherical band. Furthermore, each one of the working portions of the spherical head is engaged in a very brief cutting sequence under the conditions of the abovesaid continuous replacement of these portions, as brief as fractions of a second, and, therefore, have no time to heat excessively. This enhances the cutting conditions, additionally promotes the stability of the tool and the quality and finish of the surface being machined. The manifold incrsase of the stability of the tool, in its turn, yields an improved machining accuracy, owing to the recluced dimension-wise wear, and also enables to step up the efficiency and productivity.
Owing to the blades being inclined relative to the meridian plane of the spherical head, there have been provided the necessary prerequisites for machining either the entire perimeter of a hole, or else a part thereof, depending on the preset angle of inclination of the blades, with the spheri-cal head being rotated on the journal by sheer engagement with the bore or hole being machined, which obviates the need in a special drive for rotating the head. The field of appli-cations of the tool has been e~panded, too, owing to the tool being suitable for machining faceted holes. Furthermore, the stability of the tool has been additionally enhanced, thanks to the increased length of the blades, limited by a spherical band defined by a central angle equalling 2cf.
A somewhat unexpected side effect of the present invention is that the shavings are kinematically chipped in the course of a cutting operation, owing to the periodic variation of the value and sense of the angle of inclination of the blade to the vector of the cutting speed at every rota-tion of the head. This effect is particularly advantageous when relatively deep bores or holes are being machined, and the shavings are to be positively removed.
It is expedient that the blades should be defined by planar sections of the spherical head, and that each blade should extend along at least a part of an arc of a circle.
With the blades having this structure, the manu~actur-ing of the tool is simplified, same as its sharpening and resharpening.
It is useful that the blades o~ the spherical head should be arranged on the spherical surface thereof along a helical line.
This feature increases the working length of the blades, enhances the stability of the tool, improves its working conditions, e.g., by making the cutting-in more smooth.
The blades may be defined by intersection of projec-~ tions or lugs provided on the spherical head in the direction - of its meridian planes and having a profile corresponding to the required profile of a hole to be machined, with grooves ,: : :: . :: .
. :, ,, : , , extending in the spherical head at an angle to the meridian planes thereof.
The above structure of the blades enables to use the tool for machining faceted holes, e.g., for shaving the teeth of internal gears.
It is also useful that the blades should have its front or leading surfaces facing in the same direction, which simpli~ies the manufacturing of the tool, its sharpening and resharpening.
Alternatively, the blades may have their front or leading surfaces facing in different directions.
In this case, the tool is acted upon by uniform symmetrical loads in the process of operation, which enhances the machining accuracy.
Furthermore, the blades may have the rear or trailing surfaces thereof chamfered to the bac]c angle of up to -15, which provides for additional machining of the bore or hole ;~ by smoothing-out, enhances the surfaces finish and protects the blades against chipping-out.
~ 20 It may be also expedient that the spherical head - should be in the form of a lamination of discs mounted on the journal for rotation relative to one another.
With this structure, throughout a machining operation each blade is rotatable at its own optimum rate by the engage-ment with the hole being machined, which improves the cutting ;`
conditions by reducing slide speeds and enhances the stability of the toolO

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To expand the field of applications of the tool for semi-finishing and finishing of bores or holes, and also to increase the cutting efficiency, it is expedient that the journal should be a stepped one, with eccentric necks.
With the head having this structure, all the blades of the spherical head can be made to perform cutting simul-taneously throughout the operation, which enables to remove a relatively great machining allowance in the bore or hole and to step up the machining rate.
Brief description of the drawings:
FIG. 1 is a perspective general view of a multi-blade spherical tool wherein, in accordance with the invention, the blades are facing in opposite directions, FIG. 2 is a cross-sectional view of a multi-blade spherical tool wherein, in accordance with the invention, the blades (shown schematically) are defined by planar sections of the spherical surface, FIG. 3 is a general view of a spherical multi-blade tool wherein, in accordance with the invention, the blades (shown schematically) are arranged about the spherical head along a helical line, FIG. 4 is a general view o~ a spherical head wherein, in accordance with the invention, the blades are defined by intersections of lugs or projections with grooves made in the .`spherical head;
FIG. 5 is a cross-sectional view of a spherical head wherein the blades, in accordance with the invention, have their front surfaces facing in the same direction, , _ g :. . : ,. . . ~

FIG. 6 is a ~ros~-E3ectiDnal view of a spherical head wherein the blade~ accordarlce with the invention9 h~e their front ~urfaces facing in oppoæita direction3;
FIG. 7 is a p~tly lo~gitudinall~ sectional general Yi9W 0~ a spherical mu~t -blade tool wherein, i~ accordallce with the i~vention, the spherical head i:ncludes a lami~atior o~ discs;
~ IG. 8 i~ a ge~eral ~riew o~ a spheri~al multi blada ~ool wherein the journal is of a stepped structure;
FIG. 9 i~ a sectiorlal view alo~g the axi~ of the journal :~
o~ the tool ~hown in ~IG. 8;
~ IG. 10 ~hows tha tool of FIG. 8, as viewed ~rom the ènd face o~ the sphericRl head.
DESCRIP~ION OF THE ~REFERRED EUIBODID~
OF ~ IO~
~ here ls herdin disclo~ed a spherica~ multi-blade tool where~rl the spherical h~ad 1 (~IG. 1) ca:rrying the blade~ 2 i8 mounted o~ a journal 3 o~ a b.o~der or sh~k 4~ ~
~ h~ spherical head 1 ha~ ~ housi~g or bod~r 5 æhaped as a bo~ o~ rotat~on with a central bore 6 ~or moun~ing the head 1 orl t~e jour~al 3. ~he blade~ 2 o:~ the tool, defined by inter-seckion o~ their ~ront or leadi~g surfaceq 7 with the ~ear or tra~ling s~lrface~ 8 are arranged over an imagi~ary spheri¢al : ;~
~ur:~ace A and are either integral with the body 5 of the phearic~l head 1 or are fi~:ed thereon in any æuitab~e known manner.
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~ 2 ~4 The journa~ 3 of the shank 4 i~ preferabl~ cylindrical and is provided with mean~ for retaining the spherical hsad 1 in the axial directi~J ~.g. a nut 9 cooperating with the thread0d end o~ the jour~al 3. To provide for sslf-a~igning of the tool in a bore or hole 10 being machined9the ~pherical head 1 ma~ be disposed o~ the jo~al 3 ~ith a ~learance 11 ~e~t betw~en the journal 3 and the centra~ bore 6 of the body 5, or elso the jaurnal 3 itsel~ can be mounted on the shank 4 Ior limited radial displacement (the so-called 'tfloating") ~hich can be attained i~ any suitable manner of arra~gi~g ~loating too~ heads9 know~ to a person competen~ in the art.
~ hs shank 4 of the tool is preferably shaped as a body of rotat~on and has aither a tail portion (no~ shown in the drawing 2) for fa~tening it in a too~ holder or f~ange~ for securing it on a ~acep~ate (not ~hown ~ either) i~ a spind~e, or in the back stock, or in the rest, or i~ the slide o~ the machino tool (not shown)O
In accordance with the in~e:~tion, th~ blade~ 2 are inclinea relati~e to the m~ridia~ plane (~hich is the pla~e o~ the drawlng in ~IG. 2) of the spharica~ head 1. ~he spheri-cal head 1 i~ mo~nted on the journal 3 for ro~ation about the geometric axi~ Q-o o~ tha jour~al ~.
In it~ tur~, the aourna~ 3 is arrahg~d at an acute a~gle .
relative to the axis ~-~ o~ the shank 4. To provido ~or rotatio~ o~ the spherical head 1 on the jour~al 3, the bod~ 5 o~ the head 1 accommodates therein suitable ~earings : ~' , :
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129 which ean ba either anti~rictio~ or plain ones and are adapted to take up radial and thru~t loads in the course of a cuttlng operation.
~ he blades 2 of the too~ ars defined by planar sectîons o~ the spherical head 1 t~IG. 2)5 each blada eætending ove~
at lea~t a part of an arc ~C 0f a circ~e. With th~ blades 2 having this structure, the manufacturi~g o~ the tool is simpli-fied, same as its sha~pening and resharpening, which in this case can be done in al~-purpose machinos, 9.g. in all-purposa t ool grinding machina~, ~ithout the use of any spaci~ically desig~ed device~
~ he blades 2 of the spherical head 1 may also ba arranged :;:
ovsr the spherical surface thereof along a helical line DE
(F~G. 3). In this case the stability ~nd durability o~ th~
tool are enhanced, and the conditio~ of it~ cutting into ~he bor0 or holo 10 to be machined are improYed.
As a further d~velopment of the present in~entio~ to provide for machining ~a¢etod holes~ the spherical head 1 has made thereo~ projectio~s or lugs 13 (FIG~ 4) exta~ding :~
along lt meridian pl~3nes, ar~d grooves 14 e:Ete~din~; at ar a~gle to the~ meridian p~anes, the profile of the~e lugs 1~ - ~
corresponding to tha required profile of the holes to ~e ~.
machined~ ~ha blades 2 o~ the too~ in this case are defined by intersections o~ the lugs 13 with the grooves 14~ The ~ead~
i~g or front sur~ace~ 7 o~ tha ~lade~ 2 of tha tool, def~ed ,, . ~, ', : ' ' :

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by the ~rooves 14, and the rear or trailing surfaces 8 o~
~he blades 2, defined by the lug~ ~3, ~re shaped simi~ar~y to the working surfaces of a shaving tool. ~urthermore, the ~rooves 14 ma~ divid~ the ~ugs 1~ into severa~ portions, each portion being a tooth 15 which is eith~r a sharpened one or a backed~of~ one.
To simp~ify the manu~acture of the tool, its sharpen-ing and resharpe~ing~ the ~ront surfaces 7 ~IG~ 5) o~ its blades 2 are ~acing in the ~am~ directio~. ~his ~aci~itates automation of the operation of sharpening the tool.
Alternativel~, the front ~ur~aces 7 of tha b~ades 2 of the too~ may be ~acing in dif~erent directions, e~g. in oppo site directions (FIG. 6), whereby throughout the operation the tool is acted upon by sgmmetrical loads~ which enhances the accuracy of machini~g. In this ca~e the front surfa¢es 7 o~ the b~ades 2 and the rear ~urfaces 8 thereo~ can be shaped as those of a shaving tool.
~ o enhance the machin~ng quali-ty and to protect th~ bla-des 2 aga~nst chipping-out, ~he rear surfaces 8 of the b~ades 2 are pro~ided with chamfers 16 with tho ~ear or back angl~
u~ t~ about -15. Pr~erab~y, this angle equal~ 09 in wh~ch way tha accuracy of the manu~acture o~ the too~ is e~hanced.
~ he spherical nead 1 o~ the tool can be in the form o~
a lami~ation of disc~ 17 (~IG. 7) of which some can have a .~.
rounded profile providing for ~moothing-out o~ the bore or hole 10 being machinedO In this case throughout the operation~
o~i~g to the independent rotatio~ o~ each disc 17~ there are :

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: , ,' : ~ , , ' : ' self-set the minimum speeds of sliding of the blades 2 of the tool against the bore or hole 10 being machined, which enhances the stability and durability of the tool.
In the last mentioned modification, the journal 3 of the shank or holder 4 may have a stepped structure, with a plurality of individual eccentric necks or sub-journals 19 (FIG. 8), which provides for simultaneous performance of all the blades 2 of the tool in a cutting mode and thus enables to speed up the cutting and to increase the cutting depth, to say nothing of the field of applications of the tool being expanded, owing to the tool being usable not only for finishing opera-tions, but for semi-finishing ones, as well. The value of the eccentricity "e" and its direction are selected to satisfy the condition that the apices P (FIGS. 9 and 10) of the blades 2 of the discs 17 belong to the same plane perpendicular to the axis L-L of the bore or hole 10 being machined, about the perimeter thereof, with deviation from this plane wi~hin the preset distribution of the machining allowance between the respective blades 2.
~: 20 The herein disclosed spherical multi-blade tool per-forms machining in the following manner.
The shank 4 of the tool is mounted either by its tail portion or its flange, as case may be, on the faceplate, or in the spindle, or in the back stock, or in the rest of the machine tool. The drive of the machine tool is energized to rotate the workpiece or/and the tool about the same axis L-L, and to effect the predetermined axial feed. The tool is intro-, , ~ .
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duced into the bore or hole 10 o~ tha workpiece being machi~ed, wherein the spherical head 1 o~ the tool is se~f-centered, owing eitiler to the provision o~ the clearance 11 between the cantral bore 6 and the jouxnal 3 9 or else to the radial freedom -(floating) of the aournal 3 on the shank 4. ~hs engagement with the ~orkpiece sets the. ~pherical head 1 into rotation o~
the journa~ 3 o~ which the geometric aæis 0-0 extends at an acute angle ~C to the axis L-~ o~ the 8hank 4, the portions o~ the blade~ 2 of the head 1, contacting at any given moment the surfaco of the bore or hole ~0 of the workpiece being ma- ;
chinad~ continuously cha~gin~ within the confinss of an ima-ginary spherical band FGIK, owing to the oscillation or rocking o~ these por~ion~ relative to the surfaco of th~ bore or ho~e 10 within a~ angle eguall~ng 2 ~ hu~, in the position shown in FIG. 2 the po~tions o~ the blade~ 2 o~ the spherical head 1 axe workin~, having the length or extent ~1~ adjoi~ing the points F and I; upon the spherical head 1 having rotated about the ~x~s 0-0 throu~h 180~, the portions adJoini~g~ the poi~ts G ~nd E become the working ones, a~d so on. This mea~s that the stability and durabilit~ of the tool, as co~pared with the tool o~ the prior art, is increased at least as m~ times as thexe are por*ions having the lsngth or extent 1 in th~
length or e~tent o~ the arc ~C or DE o~ each respective b~ade 2 within the confi~es o~ the spherical band ~GX~ o~ the head 1 This continuous rep~acement of tho wor~ing portions of tha lades 2 o~ the tool also results in a signi~icant lowering o~

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the temperature in the cutting zone, appro~imately by 2000..
~00C., owing to the short duratio~ o~ t~e contact of a por~
tion o~ the blade with the sur~ace of the bore or hole being machined9 ~ollowed by relativel~ prolongad cooling. Al~ these feature~ combine to yield a greater e~ficienc~, quality and accuracy o~ the machini~g opsration.
The inc~ination o~ the blades 2 of the tool to the meri-dlan plane o~ the spherical head 1 pxovides ~or thei~ intsr-section with the vector of the cutting speed and ~or removi~g the shavings chips i~ the process o~ the osci~lation or rocking relative to the surface of the hole or bore ~0 being machi~ed~ :
.
This oscilla~ion is brough~ about as the outcome o~ the supe~-imposition of the respect~ve rotary motions o~ th~ spherica~
head 1 and o~ the-bore ox hole 10 about the a~es 0-0 ~nd L-~inclinad at an acute angle G~ relative to each othex. In this ~ ;;
way thers have been provided the prerequisites for machining aither the entire perimeter of the bore or hole 10, or else a portion thereo~9 depending on the pr~selected angle o~
t~e inclin~tio~ of the b~ades 2, in the course o~ the rota~
tion o~ the spherical head 1 o~ the jour~al ~, initiated by the engage~nt of theh head ~ith the bore or hole 10 being machined~ without the ~ecessity of inco~porating a sp~cia~
dri~e for rotatîng the head 1~ l'his featur3 broadens the ~COp3 o~ the possible uses o~ the tool~ to say nothin~ of tke sta-bilit~ an~ durability of the tool b~ing enhanced, owin~ to th~
extent or ~e~gth of the b~ades 2 being incrsased within the .

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co~f-Snes o.~ the spherlca~ band ~GIK~ ~urthe~more, there i8 effected ~inematic chipping of the shaving produced b~ the cutting9 owing to the periodic ~ariation of the value and sense of the aD$le o~ i~clinatio~ o~ the b~ades 2 ~e~ative to the ~ector o~ the cu~ting speed~ durin~ each xotation of the ~pherical head 1.
Both whan the tool with the blades 2 defined b~ the pla nar section~ of the spherical head 1 and exte~ding alo~g a part of the arc BC (~IG~ 2) or a circle is used9 and ~hen the too~ ha~ it~ b~ades 2 arranged about the spherica~ sur-fa~e o~ the head 1 along a helical line D~ (FIG, 3)9 the ma-chinin~ of the bore or hole 10 is effected in its planar sec-tion perpendicu~ar to the axis ~-~ o~ the shank 4 and exte~d-ing through the ce~tre of the sphexica~ band FGI~, with devia-tions from this p~anar section wi~hi~ th~ predetermined distri-butio~ of the machinin~ allowancs or feed betwee~ the blades 2~ In the first-mentioned case th.ere is used the multi-blada tool operating similarl~ to a countersink, a re~m~r or a ~Yi:ng ~041; in the other case it is possible to use even :~
a singla-blade tool h~ving its blade engaging tha perLmeter of the bore or hole 10 being machined in many poi~t3; which .: ~
ma~es the cutting-in of the tool more smooth and enhances the stability of the tool.
I~ cases ~here faceted holes 10 are to be machined,th0re is used the tool wherein the bladeq 2 are defined by inter~
sections of tha lugs or proaections 13 on the spherical head : i~ the direction of its meridian planes, having a profile . ~ :
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L2~4 of the hole 10, corresponding to the required profile with the grooves 14 extending in the spherical head 1 at an angle to these meridian planes. The spherical head 1 of the tool is introduced into the hole 10 being machined, into engagement therewith along an arc of up to 360, the axis 0-0 of the journal 3 is made to either cross or intersect the axis of the hole 10, and the cutting operation is performed continuously, owing to the oscillation of the lugs 13 with respect to the surface of the hole 10. The operation is continued with either the tool or the workpiece being axially fed, until the required length or depth of the hole 10 is machined.
When the tool with the blades 2 having their front surfaces 7 facing in the same direct:ion is operated, throughout the operation each blade 2 performs cutting during the first half-rotation of the spherical head, and smooths out the sur-face of the bore or hole 10 of the wor~piece during the second half of this rotation, this smoothing-out being effected by the chamfexs 16 provided on the rear surfaces 8 of the blades ~- 2, and having the rear or back angle from 0 to about -15~.
To enhance the machining accuracy, the tool can be operated, having the blades 2 of which the front surface3 are facing in different, e.g., opposing directions. In this case, notwithstanding the fact that each blade 2, same as in the pre-viously described case, cuts during one half-rotation of the head 1 and smooths out during the other half-rotation, the machining is performed under the conditions of symmetrical loads applied to the spherical head 1, owing to the opposing indexing of ; .:

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the front surfaces 7 of the blades.
The stability and durabi~ity of the tool can be additio-~a~ly enha~ced b~ the use o~ the spherical head 1 in the ~orm o~ a lamination o~ the disc~ 17 mounted on the journal 3 ~or rotatio~ re~ativ~ to one anotherO In this ca~e the discs 17 are rotated b~ the engagement with the surface of the bore or hole 10 of the workpiece being machined independentl~ of one another, and th~s are self-set to tha minimum speed o~
~rictio~ betwee~ the b~adss 2 and the bore or hole 10~
Furthermore, i~ the disc~ 17 are mounted o~ the journal 3 with tha eccentric necks or sub-journa~s 199 each disc inde-pende~t~y and a~ discs jointl~ perform cutting of the bore or hole 10 being maehined without smoothing ou~ ths surface of the latter.
This steps ~p the machi~ing rate and broade~s the ~ie~d of application~ of th~ too~ which in thi~ ca~e i~ u~able both ~or ~iniRhing and semi-fini~hin~ machlning operations.
A~though the pre~erred-embodiments of the present inv~n-tio~ ha~e been de~cribed hereinabove, it should be understood that numerou~ modifications ca~ be irLtroduced into the tools illustrated i~ the appended drawi~gs and described herei~-abo~e, wi~hout depaxting :Erom th~ spirit ar~d scope o~ th~
preact inventioll~ as set :~orth in the claims to :~ollow.

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Claims (9)

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

1. A spherical multi-blade tool for machining bores and holes, comprising: a shank; a journal extending at an acute angle relative to the axis of said shank; a spherical head mounted on said journal for rotation about the geometric axis of said journal; blades provided on said spherical head and inclined relative to the meridian planes of said spherical head.

2. A spherical multi-blade tool as set forth in Claim 1, wherein said blades are defined by planar sections of said spherical head, each one of said blades extending along at least a part of an arc of a circle.

3. A spherical multi-blade tool as set forth in Claim 1, wherein said blades are arranged on said spherical head along a helical line.

4. A spherical multi-blade tool as set forth in Claim 19 wherein said blades are defined by intersection of lugs made on said spherical head in the direction of the meridian pla-nes thereof and having a profile corresponding to the requir-ed profile of the hole to be machined, with grooves extending on said spherical head at an angle to the meridian planes.

5. A spherical multi-blade tool as set forth in Claim 1, wherein said blades have the fron surfaces thereof facing in the same direction.

6. A spherical multi-blade tool as set forth in Claim 1, wherein said blades have the front surfaces thereof facing in different directions.

7. A spherical multi-blade tool as set forth in Claim 1, wherein said blades have the rear surfaces thereof provided with chamfers having the back angle of up to about -15°.

8. A spherical multi-blade tool as set forth in claim 1, wherein said spherical head includes a lamination of discs defining said blades about the periphery of said head, the discs being mounted on said journal with provisions for their rotation relative to one another.

9. A spherical multi-blade tool as set forth in claim 8, wherein said journal is of a stepped design and defines a plurality of eccentric necks.