US1937418A - Die head - Google Patents

Description

Nov. 28,1933; L; G. WARREN 7,

DIE HEAD Filed May '19, 1932 2 Sheets-Sheet 1 .z jo 3 0: CHAsER AND CHA$EERECESS INVENTOR B Gan-@5- /e mw m ALATTORNEYJ Nov. 28, 1933. WARREN 1,937,418

0m HEAD Fild May 19, 1952 v 2 Sheets-Sheet 2 D INVENTOR b ATTORNEX:

Gil

Patented Nov. 28, 1933 PATENT OFFICE DIE HEAD Levi G. Warren, West Haven, Conn., assignor to The Eastern Machine Screw Corporation, New Haven, Conn., a corporation of Connecticut Application May 19, 1932. Serial No. 612,350

27 Claims. (01. 10- 35) -My invention relates to thread cutting die heads and more particularly to die heads of the self-opening type and to improvementsin chasers and carriers therefor. The present appli- 5 cation is a continuation in part of my application Serial Number 513,930, filed February '6,-

Heretofore it has been customary to provide die heads with thread cutting chasers which are adapted to be resharpened by grinding after becoming dull; but due to many factors hereinafter pointed out the resharpening of chasers is expensive and the results obtained by the use of such chasers is often unsatisfactory. One of the principal objects of the invention is, therefore, to provide a die head of the type adapted to cut threads on stock 'of different diameters with chasers which can be made so inexpensively that from the standpoint of cost and the quality of work produced they may be discarded and replaced by new ones more economically than chasers of the character now in use may be resharpened.

Another object of the invention is to provide an improved carrier for supporting the chaser.

A further object of the invention is to provide improved means for immovably securing the chasers in the carriers.

Still another object of the invention is to provide improved means for retaining the carriers in the die head and for initially aligning them with their operating means.

A primary feature of the invention consists in providing a die head with a plurality of sets of carriers adapted to be selectively associated with the body member of the head in grooves formed in the latter, the carriers being formed intermediate their side walls with chaser receiving slots of substantially the same width, the slots in the carriers of one of said sets being respectively spaced a greater distance from the longitudinal axis of the carrier receiving grooves of the body member than the slots in the carriers of another of said sets so that the cutting edges of the chasers adapted to be associated with each set of carriers will be spaced different distances ahead of diametral lines of the stock to becut.

' Another feature of the inventionconsists in mounting and securing the chasers in the carrier in such manner that they may be readily inserted therein ,and removed therefrom with;- out removing the carriers from the die head. Another .feature of the invention consists in providing the body member of the die head which is formed with a plurality of grooves in the front face thereof for receiving chaser carriers with forwardly projecting ribs adjacent the grooves, said ribs respectively overlapping the rear sides of the carriers to obtain an increased hearing or support for the latter.

A further feature of the invention resides in providing improved means employinga camming or wedging action to rigidly secure the chasers in the carriers.

A still further feature of the invention consists in providing detent means for cooperating with the carriers to position the latter in the die head to enable the members for actuating the carriers to initially cooperate with the latter.

.Other and more specific features of the in- 'vention residing in advantageous forms, combinatipns and relations of parts will-hereinafter appear and be pointed out in the claims.

In the drawings illustrating a preferred embodiment of the invention, Figure 1 is a side ele- I vational view of the die head with parts thereof broken away.

Figure 2 is a front view of the die head.

Figure 3 is a front view of the body member of the die head with the chaser carriers and other elements removed.

Figure 4 is a front view of the die head with' the body member removed, the shank of the body member being shown in section.

Figure 5 is a side elevational view of the body 35 member. 1

Figure .6 .is a sectional view of the die head parts thereof being shown in elevation.

Figure 7 is an enlarged front side elevational view of one of the carriers and its associated chaser.

Figures -8 and'9 are sectional views taken onlines 8-8 and 9-9 respectively of Figure '7.

Figure 10 is a detail sectional view taken on line 10-10, Figure 2.

Figures 11, 12 and 13 are diagrammatic views illustrating one carrier and its chaser of each set of carriers and the locations of the chaser receiving slots of the carrier with respect to a 0 diametral line of the work.

Figure 14 is a diagrammatic plan view of one of the chasers.

Die heads as at present constructed for operating on stock of different diameters are subject to the disadvantage that they are designed to receive relatively expensive chasers intended to be resharpened a number of times by grinding. Due to the extreme precision required in cutting threads meeting the rigid specifications of today no and because chasers'are used in'sets and those 2 eague used and the skill of the operator, considerable difiiculty is encountered in matching the chasers of each set; also, the chasers are sometimes burnt in grinding and the ground surfaces are often rough and uneven thereby decreasing the life of the chasers, reducing the quality of the threads out by the chasers and causing decreased-production. Moreover, the grinding of chasers often involves the loss of the use of the die head during the time required to grind the chasers and to check them. To avoid considerable expense ,due'

to the loss of time in setting up and breaking down the grinding machine, an individual machine must be kept in special adjustment for grinding each kind of chaser.

To allow for the resharpening of chasers by grinding they are made considerably larger than would otherwise be necessary. Taking into consideration the precision required in cutting threads, it is necessary to maintain in correct balance the various structural characteristics of a properly designed chaser. This, however, as a general rule is impossible of accomplishment in chasers to be resharpened by grinding because account must be takenof the eifect produced by the removal of metal from the chaser by the grinding operation. It is, therefore, not un usual to encounter serious difficulty in cutting even and true threads with'reground chasers.

Due to these things and especially due to the cost of the necessary grinding machinery and of training the operators thereof, it will be appreciated that the resharpening of chasers is expensive and that because of the difliculty of accurately grinding the chasers and of matching them in sets the results obtained by the use of those which have been resharpened are unsatisfactory.

My invention permits stock oi different diameters to be operated on by a die head employing chasers which upon becoming dull, may economically be discarded instead of being resharpened by grinding. To render this possible the chasers are of minimum thickness as well as of minimum size in all other respects, being preferably only of sufiicient size to have adequate strength for withstanding the cutting strains to which they may be subjected. Taking into account the difference in cost between such chasers and the relatively large ones which are designed to be curacies' now required,'because no consideration need be given concerning what happens after portions of the chaser are. removed in regrinding.

In carrying out my invention I provide the die head with a body member 1 with which is integrally formed a rearwardly extending shank 2 for connecting the head to any suitable machine. Slidably mounted on the shank is a collar member, 3 having a' radially disposed threaded openingfor receiving a screw 4, the inner end of which is adapted to extend within a longitudinally extending groove 5 in the shank 2 for limiting relative sliding movement between the body member 1 and the collar 3. The collar may be immovably held with'respect to the body member by latching means comprising a pin 6 extending rearwardly from the body member and adapted to project into an opening 7 in the collar. Movable transversely of the axis of the collar is a spring pressed lever 8 which normally projects into the opening 7 to overlappingly engage a shoulder 9 on the pin 6 for locking the collar and body member together. One end of the latching lever 8 normally projects beyond the periphery of the collar into an annular groove 10 formed on the springs 14 are preferably employed. These u springs are respectively disposed in registering openings formed in the collar and body members, and to prevent them from collapsing laterally, centering pins 15 which extend beyond the rear face of the body member, may advantageously be concentrically disposed in the openings of the latter.

The front face of the body member is iormed with a plurality of grooves 16 'for receiving the chaser carriers 17. Each 0! the grooves intersects the axial work or stock receiving opening 18 of the head and the longitudinal axis of each is preferably disposed radially with respect to the opening 18. The front side of each of thecarriers is provided with an inclined recess 19 for receiving a laterally projecting inclined lug 20 which may advantageously be formed integrally with a stud member 21 projecting forwardly from the collar member and adapted to extend within an aperture 22 formed in the body member and intersecting the carrier receiving groove 16 thereof. As the recesses 19 and their cooperating lugs 20 are inclined with respect to the longitudinal axis of the collar 3 and also the head 1, it will be appreciated that when the collar moves axially with respect to the body member the carriers 1'7 will be moved either toward or away from the work receiving opening 18 depending upon the direction of movement of the collar with respect to the body member.

., 1%! Since the inclined lugs 20 or the stud memhere 21 are disposed in the carrier receiving grooves 16 whenv cooperating with the carriers 1'7, it is necessary in assembling the die head that the carriers be disposed within the grooves before the collar may be moved into locking engagement with the body member. Moreover. even after the carriers are disposed within the grooves 16 the collar cannot be moved into looking engagement with the body member unless the carriers are so positioned in the grooves that their inclined recesses 19 'areproperly disposed to receive the cooperating lugs 20 on the stud members 21. To position the carriers in the grooves 16 so that the lugs 20 may initially enter the recesses 19 and thereby facilitate assembly of the die head; the body member is provided with a plurality of spring pressed detent means disposed within openings 23 which respectively intersect the bottoms of the carrier receiving grooves 16, Each of the detent means preferably comprises a ball or the like 24 which is normally urged forwardly into the opening 23 by a coil spring 25 so as to project slightly beyond the bottom wall of the adjacent groove 16. The diameter of the openings 23 where they intersect the bottom walls of the grooves 16 are of smaller diameter than the balls 24 to prevent the latter from moving entirely out of the openings, and the tension on the springs 25 may be controlled by screws 26 which also serve to close the opposite ends of the openings. The underside of each carrier is provided. with an indentation or recess 27 into which the ball of the adjacent detent means is adapted to project. The indentations in the carrier are so positioned that when the balls 24 project thereinto as can easily be determined by the operator upon reciprocating the carriers in the grooves, the inclined recesses in the carriers are in correct positions to receive the inclined lugs 20 on the operating members 21.

Inorder that the carriers may be held by the stud members 21 in slightly different positions of adjustment-so that theymay cooperate with stock of different diameters within a limited range, the latching pin 6 is adjustably mounted in the body member 1 by means of a screw 28. By rotating the screw, the head of which projects beyond the front face of the body member, the pin 6 may be moved axially whereby the head and collar may be held together in a plurality of positions of adjustment to maintain the carriers in different operating positions in the grooves.

- For retaining the carriers in the grooves 16 a plurality of segmental plates 29are secured to the front face of the body member intermediate the grooves by a plurality of screws 29a. Each of the plates 29 has-a portion overhanging the adjacent groove 16 which is adapted to extend into a groove 30 formed in the front or leading side of the cooperating carrier intermediate the upper and lower edges thereof and extending longitudinally of the carrier from one end thereof to the other. Ach'acent the side of each groove opposite to the side thereof beyond which the adjacentsegmental retaining plate 29 projects, the body member 1 is preferably integrally provided with a forwardly projecting rib 31 having one wall thereof flush with the adjacent side of the groove and adapted to overlappingly engage the rear or following side of the associated carrier. These ribs provide an increased support for the rear side of the carriers'a'nd therefore an extended area to which cutting strains imparted to the carriers may be transmitted. Instead of having the ribs project beyond the outer faces of the segmental retaining plates 29, they preferably terminate flush with those faces. It will be readily appreciated that by providing the headwith integral ribs affording an increased support for the chasers a better. construction results than if the ribs were omitted and the .ends of the segmental plates adjacent the ribs were continued so as to be flush with the adjacent walls of the grooves because considerable difliculty would be encountered in having the ends of the plates in exact alignment withthe sides of the grooves.

Each of the carriers 17 has a portion projecting forwardly from its associated retaining plate provided with laterally spaced portions 32 and 33 defining a chaser receiving recess 34 whose longi- 'tudinal axis is parallel with the longitudinal axis to be disposed'an'd'consequently also parallel with cured to the carrier in any suitable manner suchas by pins 36. Thus the chaser receiving recess has an end wall 37, front side and rear side walls 38 and 39, respectively, and a bottom wall 40 formed by the upper edge of the filler member 35. By slotting the carrier from one end thereof to the other and inserting the filler member 35 and of plate-like form. Moreover, they are of minimum thickness as well as of minimum size in all other respects, being preferably only of sufficient size to have adequate strength for withstanding the cutting strains to which they may be subjected. Inorder that the chasers may fit rather snugly within the recesses of the carriers, the latter are only wide enough to permit the chasers to be readily inserted therein and removed therefrom. The inner end of each chaser and the bottom wall thereof respectively conform to and are adapted to engage with the end wall 37 and the bottom wall 40 of the recess 34 in the carrier. Each of the chasers is r'emovably. secured in the recess of its carrier by a screw 41 which extends transversely of the recess. The screw is provided with a threaded portion 42 adapted to extend within andcooperate with an interiorly threaded opening in the spaced portion 33 of the carrier and is also provided with a cylindrical portion 42 adapted to extend within an opening in the spaced portion 32, said last-named opening being only of slightly greater diameter than the diameter of the head. The chaser is formed with an opening 44 through which the screw is adapted to extend, said opening being of greater diameter than the threaded portion 42 of the latter but of less diameter than the head portion 43. The distances from the axis of the opening 44 in the chaser to the inner end and bottom wall thereof are respectively greater than the distances from the axis of theconcentric openings in the spaced portions 32 and 33 of the carrier to the end wall 37 and bottom wall 40 of the rethe carrier. Intermediate its portions 42 and 43,

the screw is provided with a preferably conical portion 45 affording a wedging surface adapted to cooperate with a beveled portion 46 surrounding the opening in the chaser is eccentric with respect to the axis"of the openings in the carrier and, therefore, eccentric with respect to the axis of head 43 of greater diameter than the threaded 4 will be eccentric with the axis of the openings in v the opening 44 in the chaser. Since the axis of the screw, it will be perceived that when the screw is rotated to secure the chaser in the carrier, the

former will be forced into intimate engagement with not only the rear wall 39 of the recess but also with the endwall 37 and the bottom wall I 40 thereof. 'Thus the chaser is rigidly secured in wedging forces set up by the screw is furnished by the carrier. Furthermore, since the chaser se- 5 curing screws are located outwardly of the segmental retaining plates 29, the chasers may be easily and conveniently removed from and replaced in the, carriers without the necessity of removing the carriers from the body member or of removing the segmental plates 29.

The front side of each chaser is provided with a cutting face 47 disposed at an angle to the radial line of the work receiving opening 18 which is parallel with the longitudinal axis of the chaser, the angle given to the cutting face being known as the hook angle and designated by the refer- .ence letter .b in Figure 14. The forward'end of the chaser is serrated to form lands or teeth extending at an angle to a line normal to the radial line of the work receiving opening 18, the angle at which the lands are disposed being known as the relief angle and designated by the reference letter a in Figure'14. At its outer end the cutting face intersects the teeth or lands in a cutting edge while at its inner end it terminates in a shoulder 48. Although the cutting face is disposed at a uniform hook angle the cutting shoul -der inclines upwardly and rearwardly from the cutting edge whereby the cutting face preferably "progressively increases in width from adjacent the lower to the upperend of the chaser. By forming the cutting face in this fashion it is of maximum width adjacent the chamfer end of the chaser at which point the cutting is principally done, while at the lower end of the chaser where little if any of the metal is removed from the stock being operated upon, it is of minimum width. In order that the spaced portion 32 of the carrier which overlaps the front face of .the chaser will not extend beyond the cutting shoulder thereof and to assist in' the disposal of metal cut from the stock, the forward edge of this portion is inclined rearwardly and upwardly'in a plurality of intersecting planes as indicated at 49. It should be noted that the spaced portion 33 of the carrier which overlaps the rear face of the chaser extends beyond the forward edge of the spaced portion 32 so as to provide adequate support for the chaser.

To obtain proper cuttingaction, the cuttingedge of each of the chasers should be spaced a predetermined distance ahead of center, that is, ahead of the line passing through the center of the stock to be cut and parallel with the axis of the chaser receiving recess 34in the carrier. In Figures 11, 12, and 13 of the drawings, this line is designated by DD. This distance that the cutting edge of a chaser should be spaced above center for a given relief angle varies with the diameter of the stock to be operated on. Thus, for example, for a given relief angle, the cutting edge of a chaser for cutting threads on stock of three quarters of an inch in diameter should be spaced ahead of center a greater distance than the cutting edge of a chaser for cutting threads on stock of, say, three-eighths of an inch in diameter. The varying distances the cutting edges of the chasers should be spaced ahead of center to cut threads on stock of different diameters may be easily compensated'for when using the relatively large chasers which are designed to be resharpened because the distance between the cutting edges and the longitudinal axes or rear faces of the chasers may be varied but since the chasers of the present invention are of minimum thickness it is not possible to compensate for the varying distances their cutting edges should be spaced ahead of center" in this manner.

However, by my invention chasers of minimum thickness may be used in a die head adapted to operate on stock of a comparatively wide range in diameter. This desirable result is attained by providing the die head with a plurality of sets of carriers which are adapted to be selectively disposed in the grooves 16 in the body member 1. -Although any number of sets'of carriers may be provided for association with the die head, for purposes of illustrating the invention, the die head shown is designed to receive only three sets of carriers, one carrier of each set being i1- lustrated in Figures 11, 12, and .13 respectively. The carrier illustrated in Figure 11 is the one heretofore described and identified with the reference numeral 17 while the carriers illustrated in Figures 12 and 13 are respectively identified by the reference characters 17a and 17b. As may be observed the structuraldetails of carriers 17a the respective carriers and consequently also from the longitudinal axes of the carrier receiving grooves 16 and from the line designated D--D in the drawings. Upon referring to the drawings it will be seen that the chaser receiving recess 34 of the carrier 17, illustrated in Figure 11, is substantially coincident with the line D-D while the chaser receiving recess 34a of the carrier 17a, illustrated in Figure 12, is spaced slightly to the left of the line D--D and the chaser receiving recess 34b in the carrier 17b, illustrated in Figure 13 is spaced a still greater distance from the line D-D. Thus, since the chasers are of uniform thickness the cutting edge of the chaser illustrated in Figure 12 is spaced ahead of center a greater distance than the cutting edge of the chaser illustrated in Figure 13 and the cutting edge. of the chaser illustrated in Figure 11 is spaced 9. still greater distance ahead of center. By this arrangement it will be perceived that the die head is provided with three different sets of carriers each of which is adapted toreceive a set of chasers for operating upon stock of a different diameter. 7 I

In order that it will not be necessary to provide a different set of chaser carriers for each *difierent size threadtobe'cut-and to enable substantially all standard threads within a comparatively wide range of diameters to be cut by a single die head, the thickness of the chasers although being practically a minimum is nevertheless sufiicient to permit the distance between the cutting edges .and the rear faces of the chasers to be varied within very narrow limits so that each set of carriers may receive a plurality of sets of chassis for cutting threads on stock within a limited diameter range. Thus, one set of carriers is adapted to receive a plurality of sets of chasers for cutting threads on stock within one limited diameter range while another set of carriers is adapted to receive a plurality of sets of chasers for cutting threads on stock within still another limited diameter range and so on. For example, the carrier illustrated in Figure 11 is adapted to receive a plurality of chasers for respectively cutting threads on stock from thirteen-sixteenths of an inch in diameter to one inch in diameter, inclusive; the carrier illustrated in Figure 12 is adapted to receive chasers for cutting threads on stock'from nine-sixteenths of an inch in diameter to three quarters of an inch in diameter, inclusive; and the carrier illustrated in Figure 13 is adapted to receive chasers for cutting threads on stock from three eighths of an inch in diameter to one half an inch in diameter, inclusive.

The height that the cutting edge of the chaser for any particular carrier should be spaced ahead of the longitudinal axis of the chaser receiving recess therein so that it will be disposed in the proper cutting position with respect to the work is equal to the amount the longitudinal axis of the chaser is offset with respect to the line DD, plus the radius of the thread to be cut by the chaser multiplied by the sine of the relief angle and also plus the depth of the thread multiplied by the quotient obtained by dividing the sine of the hook angle by the cosine of the sum of the relief angle and the hook angle. Stated otherwise, the height of the cutting edge above the rear side of the chaser is equal to sin b cos (b +a) where D is the diameter of the thread to be cut,

. a the relief angle, B the distance between the longitudinal axis of the chaser receiving slot and theline DD, H the depth of the thread, E one half of the thickness of the chaser, and b the hook angle. Each of these characters is shown applied to the diagrammatic view of the chaser shown in Figure 14.

Not only are the chasers for the different sets of carriers of the same thickness but they are also preferably of equal length as well as of equal .height or' depth. Furthermore, the chaser re ceiving recesses in the carriers of each of the several sets are preferably of equal length so that each chaser will project beyond the forward end of its carrier substantially the same amount. In this manner the moment arm of the bending forces incident to the cutting strains transmitted to the projecting portions of the chasers of all of the carriers will be the same. As'the chasers of the various sets of carriers are idapted to cut threads of different diameters, the cutting edges of the chasers of the several sets of carriers must be spaced different distances from the longitudinal axis of the work receiving opening 18 of the die head. To accomplish this and at the same time to permit chasers of equal length to be used with the different sets of carriers which have chaser receiving recesses of equal length, the inclined recesses (19, 19a and 19b) in the front walls of the carriers of the different sets are respectively located unequal distances from the forward ends of the carriers. In this manner the forward ends of the carriers of the different sets, and consequently the cutting edges of the chasers therefor, will be spaced unequal distances with respect to the longitudinal axis of the work or stock receiving opening because the inclined recesses of all of the carriers, since they cooperate with the carrier actuating members 21, are disposed in approximately the same relative position with respect to the head. Upon referring to the drawings it will be observed that carrier 17a, which is adapted to receive a chaser for cutting threads of greater diameterthan the chaser of carrier 17?),

axis of the stock or work receiving opening 18 than the cutting edge of the chaser of carrier 17b. Likewise, as carrier 17 is adapted to receive a chaser for cutting threads on stock of greater diameter than the chaser of carrier 17a, the distance'between the forward end of carrier 17 and the inclined recess 19 thereof is less than the distance between corresponding parts of carrier 17a so that the cutting edge of the chaser of carrier 1'7 will be spaced a greater distance from the longitudinal axis of the work receiving opening than the cutting edge of the chaser of carrier 17a. The different distances the cutting edges of the various sets of chasers for each separate set of carriers must be spaced from the longitudinal axis of the work receiving opening is, of course, compensated for by properly adjusting screw 28 heretofore described. By constructing the carriers of the different sets so that chasers of uniform size may be used therewith, it will be readily appreciated that the manufacture of blanks from which the chasers are made is greatly simplified and the production costs of the chasers themselves are considerably reduced.

From the foregoing it will be observed that I have devised means enabling die heads for cutting threads on stock of a comparatively wide range in diameter to use chasers of such size that it will be more economical to discard them upon becoming dull than it will be to resharpen by grinding the relatively large chasers with which die heads as at present constructed are generally provided. Moreover, not only will the use of such chasers eliminate the expense incident to resharpening but the unsatisfactory work often produced by the use of resharpened chasers will also be eliminated.

I claim,

1. In a die head adapted to cut threads on' stock of different diameters, the combination with a body member having an axial work-receiving opening and having a plurality of carrier-receiving grooves intersecting said opening, of a plurality of sets of carriers adapted to be selectively associated with said body member in the grooves thereof, said carriers being respectively formed intermediate the side walls thereof with chaserreceiving slots of substantially the same width, 8; set of chasers for each of said sets of carriers, each of said chasers having a portion of substantiallythe same width disposed in the slot of its cooperating carrier and the slots in the carriers of one of said sets being respectively spaced a greater distance from the longitudinal axes of the carrier-receiving grooves of said body member than the slots in the carriers of another of ing opening and having a plurality of substantially identical grooves intersecting said opening, of a plurality of .sets of carriers adapted to be selectively associated with said body member in the grooves thereof, and a set of chasers for each set of carriers, each of said carriers being of substantially the same width and each being provided intermediate the side walls thereof with a chaser-receiving slot, said slots being of substantially the same width and the slots in the carriers of different sets being spaced unequal distances with respect to corresponding side walls of the carriers.

X adapted to be disposed in the slot of its cooperating carrier, the slot of each carrier having an axis substantially parallel with the axis of the groove in which the carrier is adapted to be disposed and the said axes of the slots in the carriers of different sets being spaced unequal distances from the said longitudinal axes of the grooves. v

4. In a die head adapted to cut threads on stock of diflerent diameters,.the combination with a body member having an axial work-receiving opening and having a plurality of substantially identical grooves intersecting said opening, a plurality of sets of carriers adapted to be selectively associated with said body member in the grooves thereof, a set of chasers for each set of carriers,

each of said carriers being provided intermediate the side walls thereof with a slot of substantially the same width and each chaser having a portion of substantially the same width adapted to be disposed in the slot of its cooperating carrier,

I the slot of each carrier having an axis substantially parallel with the-longitudinal axis of the groove in which the carrier is adapted to be disposed, said axes of the slots in one set of carriers being respectively coincident with the longitudinal axes of said grooves and the said axes of the slots in another of said sets of carriers being respectively spaced from the longitudinal axesof said grooves. v

5. In a threading die head, in combination, a body member having an axial work-receiving opening and a plurality of carrier-receiving grooves, carriers movably mounted in said grooves,

each of said carriers being provided with a slot for receiving a chaser, and chasers respectively disposed in said slots, each of said chasers having parallel sides and bei'ngprovided with a land disposed at a predetermined relief angle and also being provided with a cutting face disposed at a v predetermined hook angle, said land and cutting face intersecting in a cutting edge which'is spaced from the rear side of the chaser for a distance substantially equal to thealgebraic sum of the following distances, namely: (1) the radius of the thread to be-cut multiplied by the sine of the relief angle; (2) the distance of the center line of the chaser from the radiahline of said workreceiving opening parallel thereto; (3) the distance from the rear side of the chaser to the center line thereof; and (4) the depth of the thread to be cut multiplied by the quotient of the sine of the hook angle divided by the cosine of the sum of the hook angle and the relief angle.

6. In a die head adapted to cut threads on stock of diflerent diameters, the combination with a body member having an axial work receiving opening and having a plurality of grooves intersecting said openings, of a plurality ofsets of carriers adapted to be selectively associated with said body member in the grooves thereof, the carriers of each set being respectively provided with chaser receiving recesses of the same length, a set of. chasers adapted to be disposed within recesses of each set of carriers,each of said chasers projecting beyond the forward end of its cooperating carrier an equal amount, and means for preventing the carriers from. moving longitudinally in said grooves away from said work receiving opening, the carriers of each set respectively having portions engageable with said means, the said portions of the carriers of the different sets being spaced unequal distances from the corresponding ends of the carriers.

"I. In a die head adapted to cut threads on stock of diiierent diameters, the combination with a body member having an axial work receiving opening and having a plurality of grooves intersecting said openings, of a plurality of sets of carriers adapted to be selectively associated with said body member in the grooves thereof, the carriers of each set being respectively provided with chaser receiving recesses of the same length, a set of chasers for each of said sets of carriers, each of said chasers being of equal length andbeing adapted to be disposed in the recess of its cooperating carrier and means for preventing longitudinal movement of the carriers within said grooves, the carriers of each set being respectively provided with portions engageable with said means, the said portions of the carriers of the diiierent sets being spaced unequal distances from the cutting edges of the chasers mounted in the carriers.

' 8. In a die head, in combination, a body member having an axial work-receiving opening and a plurality of carrier-receiving grooves, carriers respectively disposed in said grooves, each of said carriers being provided with a slot whose longitudinal axis is spaced from a parallel radial line passing through the center of said opening, and thread cutting chasers respectively disposed in said slots, each of said chasers having a land disposed at a relief angle and a cutting face disposed at a hook angle intersecting in a cutting edge and having parallel sides spaced apart a distance substantially equal to the width of the slot in the cooperating carrier, the distance between the center line of said slot and the parallel radial line passing through the center of the work receiving opening being equal to the distance between the cutting edge of the chaser and therear wall thereof minus the sum'of the following: (1) the radius of the thread to be cut multiplied by the sine of the relief angle; (2) one-half the'width of the chaser, and (3) the depth of the thread multiplied by the quotient of the sine of the-hook angle divided by the cosine of the sum of the hook angle and the relief angle.

9. A thread cutting chaser for use with a die head,said chaser having parallel sides and being provided with a land disposed at a relief angle and also being provided with a cutting face disposed at a hook angle, said land and cutting face the sine of the relief angle, plus the depthof the 'thread to be cut multiplied by the quotient ohtained by dividing the sine of the hook angle by the cosine of the sum hook angle.

of the relief angle and the l 10. A thread cutting chaser adapted for association with a die headhaving a chaser receiving slot whose longitudinal axis is parallel to and spaced from a line passing through the center of the die head, said chaser being provided with a land disposed at a relief angle and with a cutting face disposed at a hook angle, said land and cutting face intersecting in a cutting edge spaced from the median plane of the chaser a distance exceeding the amount said plane is offset from said center line of the die head by an amount substantially equal to the radius of the thread to be cut by the chaser multiplied by the sine of the relief angle, plus the depth of the thread to be cut multiplied by the quotient obtained by dividing the sine of the hook angle by the cosine of the sum of the relief angle and the hook angle.

11. In a die head, the combination with a body member having a plurality of grooves in the front face thereof, of carriers respectively disposed in said grooves, segmental plates rigidly secured to the front face of said body member for respectively retaining the carriers in said grooves, each of said carriers having a portion extending forwarglly beyond its associated retaining plate and each of said extending portions being provided with a recess intermediate the side walls thereof,

' chasers respectively disposed within said recesses, and means extending transversely of each recess said groove, the opposite side wall of each carrier being provided with a shouldered portion, segmental plates rigidly' secured to the front face of said body member respectively having portions cooperable with the shoulderedportions of the carriers for retaining the carriers in said grooves, each carrier having a portion extending forwardly beyond the adjacent retaining plate and each of said forwardly extending portions being provided with a chaser receiving slot, chasers re spectively disposed in saidslots, and means extending transversely. of said slots and located outwardly of said retaining plates for removably securing said chasers in said slots.

13. In a die head, the combination with a body member having a plurality of grooves in the front face thereof, of carriers respectively disposed within said grooves, one sideof each carrier being provided intermediate the top and bottom edges thereof with a recess extending from substantially one end of the carrier to the other, segmental plates rigidly secured to the front face of said body member'for respectively retaining the carriers in the grooves of said body member, each of said plates having a portion extending into the recess of the adjacent carrier, each carrier having a portion extending forwardly beyond its retaining plate and each of said portions being provided with a slot intermediate its sides for receiving a chaser, chasers respectively disposed in said slots, and means extendingtransversely of said slots and located outwardly of said retaining plates for removably securing the chasers in the slots.

14. In a die head, the combination with a body member having an axial work receiving opening and having a plurality of grooves in the front face thereof intersecting said opening, of carriers having front and rear sides respectively disposed in said grooves, each of said carriers being provided with a recess in the front face thereof, segmental plates rigidly secured to the front face of said body member for respectively retaining said carriers in the grooves of the body member, each of said plates having a portion extending into the recess of the associated carrier, said head be-. ing integrally provided adjacent each groove with a rib projecting forwardly from said front face in overlapping engagement with the rear side of an adjacent carrier, said ribs respectively terminating flush with the outer sides of said re taining plates, each of said carriers having a portion extending forwardly beyond its retaining plate and each of said forwardly extending portions being provided with a chaser receiving slot, chasers respectively disposed in said slot, and screw means for each of said carriers extending transversely of the slot therein for removably securing the chaser disposed in the slot to the carrier.

15. In a die head, in combination, abody member having a plurality of grooves in the front face thereof and integrally provided adjacent each groove with a rib projecting forwardly from said front face, each rib having a side wall flush with one of the side walls of the groove adjacent thereto, movable carriers respectively disposed in said grooves, and segmental carrier-retaining plates rigidly secured to the front of said body member, one end of each of said plates overhanging one of said grooves so as to be in overlapping engagement with a portionof the carrier disposed therein and the other end of each of said plates terminating adjacent the rib adjoining another of said grooves.

, 16. In a die head, in combination, a body member having a plurality of grooves in the front face thereof, movable carriers respectively disposed in said grooves, carrier retaining plates rigidly secured to the front face of said body member, one end portion of each plate extending beyond one of the'side walls of one of saidgrooves so as to be in overlapping engagement with the carrier disposed-therein and the other end portion of each plate terminating inwardly of the opposite wall of an adjacent groove, and ribs formed integrally with said body member and respectively projecting forwardly from the front face thereof in overlapping relation with the last-named ends of said plates, each of said ribs having a wall flush with and constituting a continuation of one of the side walls of an adjacent groove.

17. In a die head, in combination, a body member having a plurality of grooves in the front face thereof, carriers respectively disposed in said grooves, said head being integrally provided adjacent each groove with a rib projecting forwardly from said front face, each rib having a wall flush with one of the side walls of the groove adjacent thereto and in overlapping relation with one of the side walls of the associated carrier, the opposite side wall of each carrier being provided with a recess intermediate its top and bottom edges, and segmental plates rigidly secured to the front face of said body member for respectively retaining the carriers in the grooves of the 1 body member, each of said plates having a porspectively greater than the distances between 18. In a die head, the combination with a body member having a plurality of substantially radial grooves in the front face thereof, one of the side walls of each of said grooves being of less depth than the other side wall, carriers respectively disposed in said grooves, and segmental plates rigidly secured to the front face of said body member for respectively retaining said carriers in the grooves, each of said plates having a portion projecting beyond the wall of less depth of the groove" adjacent thereto so as to be disposed in overlapping'engagement with a portion of the associated carrier.

19. A die head involving a thread cutting chaser, a carrier having a walled recess intermediate its sides for receiving said chaser, said recess including two bottom walls afiording a seat for the chaser, and means extending transversely of and through the recess and forming the sole means for securing the chaser in fixed position with respect to said bottom walls, said chaser and carrier respectively having openings for receiving, said means, the distance from the axis of the opening in the chaser to the one edge thereof being greater than the distance from the axis of the opening in the carrier to the co-acting wall of the recess whereby said axes are eccentrically disposed when the said edge of the chaser is in engagement with the said wall of the recess, said means being provided with a portion having wedging engagement with a portion of the chaser bounding the opening thereof for forcing said edge of the chaser against and maintaining it in intimate engagement with said wall of the recess.

20. A die head involving a thread cutting chaser, a carrier having a walled recess intermediate its sides for receiving the chaser, said recess having end and bottomwalls respectively affording seats for angularly disposed portions of the chaser, and means extending transversely of and through the recess said means forming the sole means for securing the chaser in fixed position with respect to said, end and bottom walls in the latter, said chaser and carrier respectively having openings for receiving said means, the distances between the axis of the opening in the chaser and the angularly disposed portions thereof being rethe axis of the opening in the carrier and the end and bottom walls of said recess whereby the axes of said openings are eccentrically disposed when said portions. of the chasers are in engagement with said walls of the recess, said means being provided with a portion having wedging engagement with a portion of the chaser bounding the opening for exerting force on the latter in a direction transverse of said means to force said portions of the chaser against and maintain them in intimate engagement with said walls of the recess. 21. In a die head, the combination with a body member having an axial work-receiving opening and having a plurality of grooves intersecting said opening, of a plurality of movable carriers respectively disposed in said grooves, a plurality of members movable longitudinally of the body member into and out of said grooves.for actuating said carrie s, each of said members having a shouldereu portion and each of said carriers having a recess for receiving the shouldered portion of the riers.

22. In a die head, the combination with a body member having an axial work-receiving opening and having a plurality of grooves intersecting said opening, of a plurality of carriers movably mounted in said grooves, members movable longitudinally of the body member into and out of said grooves for actuating said carriers, said carriers and members respectively having cooperating portions adapted to be disposed in overlapping engagement, and a plurality of detent'means respectively cooperable with said carriers for p0- sitioning the latter in said grooves to enable said cooperating portions of the members and carriers to be initially brought into overlapping engagement. 23. In a die head, the combination with a body member having an axial work-receiving opening and a plurality of grooves intersecting said opening, of carriers movably mounted in said grooves, members movable longitudinally of the body member into and out of said grooves for respectively actuating said carriers, each 'of said members having an inclined shouldered portion and each of said carriers having an inclined recess for receiving the shouldered portion of the cooperating member, and spring actuated detent means re spectively cooperable with said carriers for positioning the latter in said grooves to enable the shouldered portions of said members to initially cooperate with the recesses of the respective carriers.

24. In a die head, the combination with a body member having an axial work-receiving opening and having a plurality of grooves intersecting said opening, of carriers movably .mounted in said grooves, a plurality of members movable longitudinally of said body members into and out of said grooves for respectively actuating said carriers, each of said carriers being provided with a recessed portion and each of said members being provided with a laterally projecting inclined shoulder adapted to extend within the recess of the cooperating carrier, and means respectively cooperable with said carriers for positioning the latter in said grooves to enable the shoulders of said members to initially extend into the recessed portions of said carriers, said means involving spring detent members mounted in saidbody member'and indentations in said carriers for respectively receiving said detent members. I

25. A thread cutting chaser for a die head having a chaser receiving recess formed with seats extending at an angle to each other one of said seats being removable and provided between said seats with an opening for receiving means to se- 1 cure the chaser to the die head, said chaser havto force said faces of the chaser into intimate chasers being adapted to cut threads on stock of different diameter, the chasers of each set being ness and of substantially uniform length and also being formed in sets of four, the chasersof each set halving thread cutting helices formed on an edge thereof said set of helices being of different pitch from those of another set whereby upon employment of different sets of carriers or chasers a wide variety of threads may be cut in stock of difierent diameters by said die head.

LEVI G. WARREN.

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