US3616522A

US3616522A - Method of making compression fitting

Info

Publication number: US3616522A
Application number: US781188A
Authority: US
Inventors: Nathan H Rudolph; Ronald G Boyd
Original assignee: All Steel Equipment Inc
Current assignee: All Steel Equipment Inc; Hubbell Inc
Priority date: 1968-12-04
Filing date: 1968-12-04
Publication date: 1971-11-02
Anticipated expiration: 1988-11-02

Abstract

THE DISCLOSURE PERTAINS TO A COMPRESSION FITTING FOR CONNECTING CONDUIT TO OUTLE BOXES AND THE LIKE IN WHICH THE BODY MEMBER IS MADE BY A SERIES OF PRESS FORMING OPERATIONS ON A TUBULAR BLANK TO DEFINE A CENTRAL UPSET PORTION HAVING A HEX CONFIGURATION, AND ROLL FORMED THREADED END PORTIONS OF DIFFERENT EXTERNAL DIAMETERS IN WHICH THE DIAMETER OF THE TUBULAR BLANK IS EQUIVALENT TO THE PITCH DIAMETER OF THE LARGE END OF THE COMPLETED BODY MEMBER, AND AN INDENTATION IS ROLLED INTO THE BLANK ADJACENT ITS SMALLER END TO DEFINE THE MAXIMUM THROAT SIZE OF THE FITTING AND STOP FOR THE CONDUIT WHEN RECEIVED IN THE BODY MEMBER LARGER END. IN MAKING THE BODY MEMBER, THE BLANK IS FORMED BY SEVERING SAME FROM THE TUBING TO INCLUDE THE INDENTATION LOCATED ADJACENT ONE END OF SAME, THE ENDS OF THE BLANK ARE DEBURRED, THE SAID ONE END OF THE BLANK IS NECKED DOWN TO APPROXIMATELY THE INDENTATION, THE BLANK IS UPSET INTERMEDIATE ITS ENDS TO DEFINE THE HEX CONFIGURATION, AND WHEN THE THREADS ARE ROLLED INTO THE BLANK ENDS, AFTER WHICH THE BODY MEMBER IS SUITABLY COATED. THE REDUCED END OF THE BODY MEMBER RECEIVES A CONVENTIONAL BOX ENGAGING LOCK NUT WHILE THE LARGER BODY MEMBER END IS EQUIPPED WITH A CLAMP NUT AND COOPERATING GLAND FOR FIXING THE CONDUIT TO THE FITTING. ALSO DISCLOSED IS A SPECIAL DIE ARRANGEMENT FOR NECKING DOWN AND UPSETTING THE FITTING BODY MEMBER.

Description

Nov. 2, 1971 Fild Dec. 4, 1968- N. H. RUDOLPH ETAL 3,616,522

METHOD OF MAKING COMPRESSION FITTING 4 Sheets-Sheet 1 w wxmw ATTO RNEYS Nov. 2, 1971 RUDQLPH ETAL 3,616,522

METHOD OF MAKING COMPRESSION FITTING Filed Dec. 4, 1968 4Sheets-Sheet z F168 INVENTORS NATHAN Hv RUDOLPH RONALD G. BOYD AT TORN EYS METHOD OF MAKING COMPRESSION FITTING Filed Dec 4. 1968 4 Sheets-Sheet 3 FIG9 I I use) \86 \64 i I 2 I70 290 148 62 I I \94 M I 50 Q I I I 3) FIG.

IO FISH IN NTORS NA N UDOLPH RON D G. BOYD ATTORNEYS Nov. 2., 1971 N. H. RUDOLPH ET AL 55 METHOD OF MAKING COMPRESSION FITTING 4 Sheets-Sheet 4.

Filed Dec. 4, 1968 INVENTORS NATHAN H. RUDOLPH RONALD G. BOYD ATTORNEYS BY W United States Patent US. Cl. 29-458 6 Claims ABSTRACT OF THE DISCLOSURE The disclosure pertains to a compression fitting for connecting conduit to outlet boxes and the like in which the body member is made by a series of press forming operations on a tubular blank to define a central upset portion having a hex configuration, and roll formed threaded end portions of different external diameters in which the diameter of the tubular blank is equivalent to the pitch diameter of the large end of the completed body member, and an indentation is rolled into the blank adjacent its smaller end to define the maximum throat size of the fitting and a stop for the conduit when received in the body member larger end. In making the body member, the blank is formed by severing same from the tubing to include the indentation located adjacent one end of same, the ends of the blank are deburred, the said one end of the blank is necked down to approximately the indentation, the blank is upset intermediate its ends to define the hex configuration, and then the threads are rolled into the blank ends, after which the body member is suitably coated. The reduced end of the body member receives a conventional box engaging lock nut while the larger body member end is equipped with a clamp nut and cooperating gland for fixing the conduit to the fitting. Also disclosed is a special die arrangement for necking down and upsetting the fitting body member.

This invention relates to compression fittings for connecting EMT or thin wall conduit to outlet boxes and the like, and more particularly, to a compression fitting in which the body member is formed from tube stock, and a method of making same.

Heretofore, compression fitting body members have been formed by employing die casting techniques or by deep drawing a flat blank, which involve sophisticated tooling, expert handling, and significant material wastage.

A principal object of this invention is to provide a method of making compression fittings from tube stock which substantially eliminates wastage and permits the use of simplified tooling.

Another principal object of the invention is to provide a compression fitting arrangement in which the body member is fabricated from tube stock by simplified and labor saving procedures.

Other objects of the invention are to provide a method of making the body member of compression fittings that is composed of simplified press forming steps which involve no significant material wastage, to provide a method of making compression fittings that is readily adapted for economical mass production purposes, to provide a die arrangement that is especially adapted for press forming the fitting body member, and to provide a compression fitting that is economical of manufacture, convenient to apply, and long lived in use.

Other objects, uses, and advantages will be obvious or become apparent from a consideration of the following detailed description and the application drawings in which like reference numerals indicate like parts throughout the several views.

In the drawings:

3,616,522 Patented Nov. 2., 1971 ice FIG. 1 is a plan-view of an outlet box having the compression fitting of this invention and a length of EMT applied thereto for the purpose of securing EMT (or thin walled conduit) to the box;

FIG. 2 is an exploded view illustrating the part-s of the fitting, the box wall to which the same is clamped, and the end of the conduit that is applied thereto;

FIG. 3 is a sectional view through the fitting as applied to the conduit end, with the box wall and lock nut omitted;

FIG. 4 diagrammatically illustrates the initial blank forming operations in which the tube stock from which the fitting body member blank is formed is processed to define the blank;

FIG. 5 is a side elevational view of the blank as formed by performing the steps illustrated by FIG. 4;

FIG. 6 is a sectional view of the blank shown in FIG. 5, on a somewhat enlarged scale;

FIG. 7 diagrammatically illustrates the next step of the method in which the ends of the blank are deburred,

with the blank being shown in section and the deburring tools being shown in elevation;

FIG. 8 is a fragmental view of one end of the fitting showing the chamfered inner edge surface that is formed of the step of FIG. 7;

FIG. 9 is a vertical sectional view, partially in elevation, illustrating the die arrangement that is employed to neck down one end of the blank and upset the mid portion of the blank to define the hex shaped mid portion of same;

FIGS. 10 and 11 illustrate the shaping that the blank takes in going through the two stage shaping procedure performed by the die arrangement of FIG. 9; and

FIG. 12 diagrammatically illustrates a dial feed die arrangement in which the die structure of FIG. 9 is incorporated.

However, it is to be understood that the specific drawing illustrations provided are supplied primarily to comply with the requirements of the Patent Code, and that the invention may have other embodiments which are intended to be covered by the appended claims.

GENERAL DESCRIPTION Reference numeral 10 of FIG. 1 generally indicates the compression fitting of this invention applied to an outlet box 12 for the purpose of securing to same conduit 14.

The box 12 is entirely conventional in nature and is intended to represent any standard form of outlet box, switch box, and other structures of this character to which the fitting 10 can be applied. Box 12 includes bottom wall 16 and side walls 18 formed with the familiar knock outs 20, each of which, when removed, defines box opening 22 (FIG. 2) to which the fitting 10 is applied.

The fitting 10 generally comprises a tubular body member 24- defining threaded

end portions

26 and 28 separated by a hex shaped median portion 30 defining a rounded flange portion 31 formed with the usual planar surfaces 32 adapted for applying a suitable holding tool to the body member 24 for holding same against movement when applying the body member to the box 12.

The body member 24 is further formed to define an annular indentation 34, forming annular ridge 35 inside same, and chamfered

surfaces

36 and 38 at the ends thereof.

Associated with the smaller end portion 26 of the body member 24 is a conventional box wall engaging lock nut 40, which is turned onto the body member end portion 26 after same has been received in an opening 22 of the box 12 to clamp the box wall involved against the body member flange portion 31, and the end 28 of the body member is proportioned to receive the end 42 of the conduit 14, which as shown in FIG. 3, abuts against the annular ridge 35, which thus forms a stop for the conduit. Also associated with the fitting are a contractable gland element 44, split as at 46, which in its uncontracted relation loosely fits over the exterior surface 48 of the conduit end 42, and which has a spherically contoured peripheral surface 50 for cooperation with chamfer 38 of member 24 and camming surface 52 of a clamp nut 54 that is threaded onto the end portion 28 of the fitting body member 24. Gland element 44 in application is lodged in annular recess 55 defined by nut 54 between its surface 52 and its threaded portion 57.

The fitting 10 may be employed to attach the conduit 14 to a box, such as box 12, by first removing an appropriate knock out to open a desired opening 22, after which the body member 24 is inserted into the opening 22 and the nut turned onto the end portion 26 of the body member 24 to clamp the box wall between it and the body member flange portion 31, which is formed to define a clamping wall 56 that serves as an abutment surface for this purpose. The nut 54 and H the gland 44 are then applied in that order to the end 42 of the conduit 14, and the conduit end 42 is inserted within the body member 24 to the position indicated in FIG. 3, after which the clamping nut 54 is drawn against and turned onto the body member end portion 24 to cam the gland element 44 into clamping relation with the conduit at its

edges

58 and 59, this action closing same firmly about the conduit to securely hold the conduit within the fitting. The gland 44 is proportioned to pass readily through the threaded portion 57 of nut 54 into its recess 55 when the latter is brought against the body member for application thereto.

The lock nut 40 may take the form of any conventional lock nut suited for the indicated purpose. Nut 54 is preferably formed from steel by a suitable screw machine operation. Gland 44 may be of any conventional metal or plastic element of the configuration indicated that will serve the clamping function described.

The body member 24 is preferably made by the practice of the method illustrated in conjunction with FIGS. 4-12.

METHOD OF MAKING THE FITTING Referring now to FIGS. 4-12, the fitting 10, and more specifically, the body member 24 thereof, is made in accordance with this invention from tube stock in the form of mild steel tubing, following the procedure indicated in FIGS. 4-12, in accordance with which a blank (FIG. 5) is formed from a length of tube stock 61 and has indentation 34 rolled therein, after which the

ends

62 and 64 of the blank 60 are deburred (FIG. 7); the blanks 60 are then consecutively applied to one of a series of lower die plate structures suitably mounted on a rotating platform 68 of a dial feed type die arrangement 66 to consecutively pass under a pair of upper die heads 72 and 78 (FIG. 9) which consecutively neck down the end 62 of the blank to approximately the area of the groove 34, as indicated at 80 of FIG. 10, and upset the blank 60 at its mid portion to define the hex surface defining flange portion 31 (see FIG. 11).

Thereafter, the

ends

62 and 64 are provided with external threads by a suitable thread rolling machine operation, after which the thus formed body member is provided with a suitable protective coating, as by electroplating with zinc following any suitable electroplating procedure.

Referring back now more specifically to FIG. 4 of the drawings, in performing the groove forming and blank cutting steps, the end 63 of the tube stock 61 from which the blank is formed is sequentially fed through a rotating chuck structure 90, past a rotatably mounted severing or cutting blade 92 and a rotatably mounted rolling blade 94, which perform the blank rolling and cutting functions indicated. The diagrammatic illustration of FIG. 4 represents a conventional cut off machine such as that made by Barton & Oliver, in which the blade 92 is journaled between the

arms

95 and 96 of a suitable head structure suitably actuated, as by a suitable hydraulic cylinder device or other conventional and suitable means for mechanically, hydraulically and/ or pneumatically actuating same to move the blade 92 toward and away from the tube stock in the manner indicated by arrow 98. Blade 92 is shaped as at 100 in accordance with standard practices to sever a blank 60 from tube stock 61 when the tube stock 61 is rotated and blade 92 is pressed against same.

Similarly, blade 94 is journaled as at 102 between the

arms

104 and 106 of a suitable head structure actuated by a suitable hydraulic cylinder device to move toward and away from the tube stock 61 in the manner indicated by arrow 108. Blade 94 is formed with a convexly rounded periphery 110 proportioned to define the indentation or groove 34 when suitably pressed against the tube stock 61 while it is rotating.

The tube stock 61 in accordance with this invention has an outer diameter that is equivalent to the pitch diameter of the threading applied to the larger end portion 64 of the blank, and has an internal diameter to closely receive and substantially complement the outer diameter of a standard size of EMT, as indicated in FIG. 3.

In performing the operations illustrated by FIG. 4, the cut ofl? machine is operated to advance and position the end 63 of the bar stock 61 where shown in FIG. 4 relative to chuck 90 and rotated, after which the groove forming blade 94 is pressed against the tube stock 61 with sutficient pressure to define indentation or groove 34 as well as ridge 35 circumferentially of the tube stock as same rotates, the minimum internal diameter of which (indicated at 35 in FIG. 3) defines the maximum throat size of the fitting. The pressures required will depend upon the specific materials and sizes being processed and can be determined in accordance with any conventional procedure used for performing a deformation of this type.

When the formation of groove 34 is nearing completion circumferentially of the tube stock, the cutting blade 92 is advanced against the tube stock 61 to sever the blank 60 from same, as at 112. After the groove 34 is completed, the blade 94 is withdrawn from the tube stock, while the cutting blade 92 remains in position to complete its cutting operation. The result is the formation of the blank 60 in the form shown in FIG. 5 and 6, in which the

ends

62 and 64 of the blank are left with a ragged inner edge where indicated at 114, which is eliminated by the practice of the chamfering step shown in FIG. 7.

Referring now specifically to FIG. 7, blanks 60 in the form they appear in FIGS. 5 and 6 are then consecutively chamfered as at 36 and 38 by having the

ends

62 and 64 applied to a pair of conically shaped

grinding members

116 and 118 rotatably mounted on their

respective shafts

118 and 120 that may be retracted and advanced in accordance with the

respective arrows

122 and 124.

The chamfering arrangement indicated in FIG. 7 is intended to represent a suitable chamfering machine for performing same, such as that made by Pines Engineering Company, in which the blanks are stacked in a chute or way and fed one by one downwardly through the machine for application to the rotating

grinding elements

116 and 118 that are automatically retracted and advanced to receive a blank 60 therebetween, grind the

ends

62 and 64 thereof to form the chamfer 36, and retract to permit the thus deburred blank to pass onto the next stage of the processing procedure.

Turning now to the press forming die arrangement of FIGS. 9 and 12, the lower die plate structures 70 each comprise a stepped diameter mandrel positioned within an annular holder 132 defining a bore 134 proportion to substantially complement the shank portion 136 of the mandrel 130. The mandrel 130 is shaped to define end portion 137 of a reduced diameter which is equilavent to the inner diameter of the end 64 of blank 60 while the bore 134 of element 132 has a diameter equivalent to the outer diameter of the blank end 64.

The holder 132 is received within mounting element 138 that is secured to platform 68 by appropriate bolts 140. Received about the upper end of holding element '132 is centering element 142.

One or more alignment pins 144 may be applied be tween the mounting member 138 and the platform 68 for die alignment purposes.

Platform 68 carries plate structure 146 that supports the mandrels 130 and their respective lower die plate structures 70 in the operating position shown in FIG. 9.

The respective blank 60 as they emerge from the chamfering procedure of FIG. 7 are consecutively applied to the respective lower die plate structures 70 at a suitable position in advance of the position of operation of the upper

die plate structures

72 and 78, with respect to the circumference of the platform 68. At the operating position of upper

die plate structure

72 and 78, the platform 68 passes over a suitable abutment structure 148 that supports the platform 68 when the upper die plate structures are applied in the manner indicated in FIG. 9.

As indicated in FIG. 9,, the individual blanks 60 are applied to the respective lower die plate structure 70 with their ends 64 received over the end portion 137 of the rnandrels 136, and within the space defined by such end portions 137 and the respective bores 134 of holding elements 132, the end 64 of the element 60 resting on the shoulder 150 as defined by the mandrel 130 at its end portion 137.

The upper

die plate structures

72 and 78 are structurally united in any suitable manner and are connected to a common hydraulically operated head structure of any suitable type. The

die plate structures

72 and 78 are spaced apart circumferentially of the platform 68 to be aligned with two adjacent lower die plate structures 70 to simultaneously perform the two indicated press forming operations of FIG. 9.

The upper die plate structure 72 comprises a die plate 152 formed with an annular forming surface 154 and is suitably secured within holder member 156 that is clamped to a suitable mounting plate structure 158 by clamp member 160 under the action of suitable securing bolts 162.

The forming surface 154 of die plate 152 is shaped to reduce or neck down the end 62 of blank 60 to the configuration indicated in FIG. 10. Associated with die plate 152 is an ejector member 164 that slidably engages within the forming surface 154 and is biased by suitable compression spring 166 to engage its holder 168 with the back side 170 of the die plate 152 in the retracted position of the die plate structure 72. Spring 166 suitably seats within a bore 172 formed in the ejector member and against spring seat 176 that is suitably positioned against mounting plate 158.

The upper die plate structure 78 comprises a shaping die plate 180 (defining a hex shaped shaping surface 181) secured to annular die plate member 182 as by appropriate screws 184, which is in turn affixed to the upper die plate mounting member 186 by appropriate bolts 188. Fixed within the die plate member 182 is annular guide element 190 defining a bore 192 having a diameter equivalent to the outer diameter of the necked down surface 194' of blank end 62. Mounted within the bore 192 of member 190 is thrust member 196 having an annular stem portion 198, the outer diameter of which is substantially equivalent to the diameter of bore 192, and which slidably receives the head portion 200 of a mandrel 202 that is fixedly mounted within mounting structure 186, as by suitable set screws 204.

Die structure 78 includes one or more stripping pins 206 that are operated to engage the thrust member 196, and that are simultaneously thrust downwardly on withdrawal of the die plate structure 78 to eject the upset blank from guide member 190 after the press forming action of the upper die plate structure 78 has been completed.

As indicated, the upper

die plate structures

72 and 78 are united in any suitable manner to form a composite upper die plate structure that has been generally designated as 210, which in turn is afiixed to the operating head of a suitable hydraulic cylinder device for forcing the composite die plate structure 210 downwardly against the lower die plate structures 70 positioned under same with sufficient force to perform the press forming operations indicated.

In operation, the dial feed arrangement of FIGS. 9 and 12 contemplates that the individual blanks 60 will be applied in a consecutive manner at a station, such as that indicated at 12 of FIG. 12, with the platform 68 being rotated in an intermittent manner to a press forming station at which the composite upper die head structure 210 operates, such as where indicated at 214 in FIG. 12. As a lower die plate structure 70 carrying a blank 60 in the manner indicated in FIG. 9 reaches the first position 216 of station 214, and platform 68 is at rest momentarily to hold the indicated lower die plate structure 70 in that position, the composite upper die plate structure 10 is lowered to bring the forming member 152 into forming engagement with the end 62 of blank 60 in the manner indicated in FIG. 9 to shape the blank 60 as indicated in FIG. 10, whereupon the head structure 210 is withdrawn, with ejector member 164 under the action of spring acting to insure that the die plate structure 70 passes freely from the blank .60 without disturbing the position of same.

The platform 68 is then actuated to move the lower die plate structure 70 in question to position 218 of station 214, this action also positioning the next succeeding lower die plate structure at position 216. When movement of platform 68 is again momentarily ceased, the composite die plate structure 210 is lowered to perform the indicated press forming operations on the blank 60 being processed; in the case of the upper die plate structure 78, the necked down end portion 62 is received within the bore 192 of holding member 190, and as the die plate structure 78 continues to lower, the terminal end portion 220 of the blank is engaged by the annular stern portion 198 of thrust member 196, which presses the blank end portion 62 downwardly, upsetting same as at 222 outwardly thereof into engagement with the hex configuration forming surface 181 of shaping member 180. The parts of the upper die plate structure 78 are so proportioned that when shaping plate member engages the lower die plate structure 70 beneath same, the upsetting deformation of the blank indicated in FIG. 9 has been completed to define the fitting blank hex shaped portion 30.

On withdrawal of the composite head structure 210, stripping pins 206 are operated by suitable hydraulic mechanisms or the like to force thrust member 196 downwardly and effect ejection of the blank 60 from holding member and shaping member 180. The ejected blanks are picked up in any suitable manner for further processmg.

Platform 68 may be automatically operated in any suitable manner to intermittently rotate same in the time sequence indicated to permit manual application of the individual blanks 60 at the station 212 and the press forming functions that are indicated for the

positions

216 and 218 of station 214.

The blanks when ejected from die plate structure 78 having the configuration indicated in FIG. 11 and at this point the ends 62 and 64 are threaded by a suitable rolling machine operation, a Reed thread rolling machine being adequate for this purpose. The ends 62 and 64 of the blank 60 may be threaded simultaneously or sequentially in any desired order, which provides the fitting body member indicated in FIGS. 1-3, that is then suitably coated with a protective finish, as already indicated.

As previously indicated, the blank 10 is formed from tube stock having an outer diameter that is the same as the pitch diameter of the threads at the blank end 64. The pitch diameter referred to is indicated by the dimension A of FIG. 3 relative to the major and minor diameters of the threading of blank end 64, indicated by dimensions B and C respectively; thus, if circles were drawn with the dimensions A, B and C, the circle defined by the dimension A would be half way between the circles defined by the dimensions B and C.

The significance of this is that the formation of the threading by rolling presses the material of the blanks 60 radially outwardly to form the major diameter of the threads, with the minor diameter of the threads being defined by indentations formed in the blank. Thus the external surface of the blank is not cut away to define the screw threads, making it possible to use tube stock of minimum OD size and thickness. The thread rolling machine procedure avoids cutting and thus saves material; further, it is a faster way of forming threading than cutting type threading procedures. In any event, this invention permits the fitting body member 24 to be formed from tube stock having an OD no larger than the pitch diameter of the threading for the larger end 64 of the blank.

In a commercial form, the pitch at the blank end 62 is 14 threads per inch while at the end 64 the pitch is 18 threads per inch. The filling is made in sizes ranging from one half inch to two inches diameter (the pitch diameter of the blank end 64) in one half inch steps for application to conduit of corresponding size.

The compression fitting is completed by the application thereto of the nuts 40 and 54 and gland 50 in the manner previously indicated.

It will therefore be seen that this invention has provided a method of making compression fittings and a compression fitting resulting from the practice of the same that significantly reduces the cost of labor and hardware to perform the method. The method steps indicated may obviously be performed by comparatively unskilled help, as compared to complex die casting and deep drawing apparatus. The only material wasted from practice of this method is that removed by the cutting of the blank 60 from the tube stock and the chamfering at 36 and 38 in deburring the blank.

The foregoing description and the drawings are given merely to explain and illustrate the invention and the invention is not to be limited thereto, except insofar as the appended claims are so limited, since those skilled in the art who have the disclosure before them will be able to make modifications and variations therein without departing from the scope of the invention.

We claim:

1. The method of making a body member for compression fittings of the type adapted to connect conduit to outlet boxes and the like, said method comprising:

forming a blank from one end of mild steel tubing having an indentation formed in same about the blanks periphery and ositioned inwardly of one end thereof approximately one third the length of the blank, deburing the ends of the blank,

necking down said one end of said blank to approximately said indentation,

upsetting said blank intermediate the ends thereof and adjacent said indentation to define a hex shaped peripheral portion about said blank,

and rolling threading into said ends of said blank.

2. The method set forth in claim 1 wherein:

8 the tubing has an outer diameter equivalent to the pitch diameter of the threading of the other end of said blank.

3. The method set forth in claim 1 including electroplating said blank to complete same.

4. The method of making a body member for compression fittings of the type adapted to connect conduit to outlet boxes and the like, said method comprising:

taking a length of tubing and rolling in one end thereof at a point spaced from the terminous of said end thereof an indentation proportioned to define the throat of the fitting,

severing a blank from said tubing one end proportioned to include said indentation spaced from said ends of said blank but positioned adjacent one of said ends thereof,

deburring the ends of the blank,

upsetting said blank intermediate the ends thereof and between said indentation and the other end thereof to define a hex shaped peripheral portion intermediate the ends of said blank,

rolling threading into the external surfaces of said ends of said blank,

and coating said blank with corrosion resisting material.

5. The method set forth in claim 4 wherein:

the tubing has an outer diameter equivalent to the pitch diameter of the threading of the other end of said blank.

6. The mehod of making a compression fitting of the type adapted to connect conduit to outlet boxes and the like, said method comprising:

deburring the ends of the blank,

rolling threading into the external surfaces of said ends of said blank to complete the formation of the body member of said fitting,

coating said body member with corrosion resisting material,

and applying a lock nut to said one end of said body member and a clamp nut and cooperating gland to the other end thereof.

References Cited UNITED STATES PATENTS 2,053,808 9/1936 Young 29 157 X 2,089,784 8/1937 Cornell 29 157 X 2,630,339 3/1953 Appleton 285158 JOHN F. CAMPBELL, Primary Examiner D. M. HEIST, Assistant Examiner U.S. Cl. X.R.

UNZTED STATES PAQENT U1 FZ'CE CERTIFICATE OF QGRRECTEON Patent Na. 3,616,522 Dated November 2, i971 Inveuwfl nmman H. Rudolnh et a1 It; is certified that error apgaeam in the abava-identified patent and that said Letters Eaten wca wan-sated m shown balms;

CClumn 1, line 2% after blank is insevt mafia from mild steel tubing fed through a cut .off machine in which the,

indentation is r'olle'd into the tubing and the blank is Column 2, line 2 for of read by Column 7, line 59, for debur'ing" mad debut-ring Column 8, line 29, for "me'l rod", read method Sign ed and sealed this 25th day of A r-11 19,72.

(SEAL) I r v tcest:

, EIJwARD M.FLETCHER',J'RV \RVOBERT GQ'TTSGHALK AtT es tingOffi'ger' V v Cbmmi s'si oner of Patents l o I