US1281675A

US1281675A - Screw-thread-cutting device.

Info

Publication number: US1281675A
Application number: US18709817A
Authority: US
Inventors: Thomas Shehan
Original assignee: Individual
Current assignee: Individual
Priority date: 1917-08-20
Filing date: 1917-08-20
Publication date: 1918-10-15
Anticipated expiration: 1935-10-15

Description

T. SHEHAN.

SCREW THREAD CUTTING DEVICE,

APPLICATION FILED AUG.20. IQH.

1,281,675. Patented Oct. 15, 1918.

3 SHEETSSHEET l.

W/fngsses. [/IYfl/or. g A I J/ T. SHEHAN.

SCREW THREAD CUTTING DEVICE.

APPLICATION FILED AUG.20.-l9l7.

Patented Oct. 15, 1918.

3 SHEETS-SHEET 2 mar.

T, SHEHAN.

SCREW THREAD CUTTING DEVICE.

APPLICATION men AUG.20. um.

1,281,675 Patented" Oct. 15, 1918.

3 SHEETS-SHEET 3.

pair

THOMAS SHEHAN, OF CLEVELAND, OHIO.

SCREW rflREAD-CUTTING DEVICE.

tasters.

Specification of Letters Patent.

Patented Oct. 15, 1918.

Application filed. August 20, 1917. Serial N 0. 187,098.

To all whom it may concern:

Be it known that I, THOMAS SHEHAN, a citizen of the United States, residing at Cleveland, in the county of Cuyahoga and State of Ohio, have invented a new and useful Screw-Thread-Cutting Device, of which the following is a specification.

This invention relates to improvements in devices for cutting screw-threads, and pertains more especially to a tap or device adapted to out internal screw-threads and comprising a cutter-head which is provided in its forward portion with substantially radially arranged guideways engaged by cutters.

One object of this invention is to produce a tap of the character indicated which comprises simple, durable, convenient and reliable improved means for shifting or adjusting the cutters simultaneously.

Another object is to provide improved means whereby the cutters, upon having completed their cutting operation, are simultaneously and correspondingly withdrawn from the work.

Another object is to provide improved means whereby the cutters, when they are in position for cutting a screw-thread, can be readily simultaneously and correspondingly readjusted for making a deeper or shallower out.

Another object is to facilitate the making and assembling of the component parts of my improved screw-thread-cutting device and to render said device reliable in its operation and not liable to get out of order.

With these objects in view, and to attain any other object hereinafter appearing, this invention consists in certain features of construction, and combinations and relative arrangement of parts, hereinafter described in this specification, pointed out in the claims, and illustrated in the accompanying drawings.

In said drawings, Figure 1 is a side view of a portion of a machine provided with my improved tap or device for cutting screwthreads and shows the object or work which is to be internally screw-threaded by said device, partly in section. Fig. 2 is a central vertical longitudinal section of said screwthread-cutting device. Fig. 3 shows a portion of Fig. 2, but in Fig. 2 the cutters are shown in their outer position ready for operation on a tubular or hollow object which to be internally screw-threaded, whereas Fig. 3 shows the cutters as having been actuated into their inner position upon the required movement of the cutter-head forwardly from the stock. Fig. 4 is a trailverse vertical section taken along the line 44:, Fig. 2, looking forwardly. Fig. 5 is a transverse vertical section taken along the line 55, Fig. 2, looking forwardly. Fig. 6 is a transverse vertical section taken along the line 66, Fig. 2, looking forwardly. Fig. 7 is a section, in detail, taken along the line 7-7, Fig. 4, looking in the direction indicated by the arrow. Fig. 8 is a transverse vertical section taken along the line 88, Fig. 2, looking forwardly. Fig. 9 is a transverse vertical section taken along the line 9-9, Fig. 2, looking forwardly. Fig. 10 is a transverse vertical section taken along the line 1010, Fig. 2, looking rearwardly. Fig. 11 is a vertical section, in detail, taken along either line 1111, Fig. 9, looking in the direction indicated by the arrow. Fig. 12 is a section, in detail, taken along the line 1212, Fig. 9, looking inwardly. Fig. 13 is a side view of a rotatable endwise shiftable member adapted to participate in shifting the cutters. Portions are broken away in the drawings to reduce their size.

Referring to Fig. l of the drawings, A indicates the bed of a machine provided with an upright standard a from which my improved collapsible tap or device for cutting screw-threads is supported. Said screwthread-cutting device comprises a stock B and a cutter-head C carrying cutters D. A work-feeding head E is shown engaging a slideway 16 formed in the bed A. Said slideway is arranged as required to enable the head E to be moved toward and from said screw-thread-outting device. F indicates a horizontally arranged spindle which has bearing in the head E and is parallel with the slideway 16 and provided with two collars f arranged to prevent endwise movement of the spindle in opposite directions independently of the head E. Said spindle is suitably rotated, and the head E is shifted endwise of the slideway 16 in any approved manner. Means for rotating a spindle while the spindle is being shifted endwise are too well known in the art to require illustration and description in this specification. Suflice it to state that the spindle F is employed as a work-holder, and 17 Fig. 1, indicates the work, such, for instance, asa tubular or hollow member which is carried by the spindle and arranged to be fed into position to be operated on internally by the cutters D. The stock B (see Figs. 1, 2, 3, 9 and 10) is arranged horizontally and has its forward end-portion larger diametrically than the remainder of the stock. The stock B is shown extending into and rigidly secured to the standard a by a suitably applied setscrew 18. The stock B is provided centrally with a horizontally arranged bore 20 extending endwise of and through the stock and having its forward end-portion larger diametrically than the remainder of said bore. Centrally and extending endwise of adjacent end-portions of the stock B and cutter-head C is a horizontal shaft or rotatable member which is circular in crosssection and has its forward portion G larger diametrically than the remainder of said rotatable member, and the rearward and diametrically smaller portion 9 of said rotatable member is arranged within and extends endwise of the bore 20 in the stock and has bearing in the stock rearward of the forward and diametrically larger endportion of said bore. The forward and diametrically larger portion G of said rotatable member is shown in Fig. 2 as a1"-' ranged wholly within and extends endwise of the rearward and diametrically larger end-portion of a bore 22 formed in and arranged centrally of and extending endwise of the cutter-head C and ha bearing in the rearward and diametrically larger end-portion of the cutter-head. The stock B and the cutter-head C. are externally circular in cross-section and arranged in line endwise and have their adjacent and diametrically larger portions corresponding in external diameter, and the

bores

20 and 22 are circular in cross-section and arranged in line endwise, and the diametrically larger or adjacent end-portions of said bores are in registry and correspond diametrically.

The forward end-portion of the cutterhead is provided (see Figs. 2, 8 and at) with guideways 25 which are arranged substantially radially of the cutter-head and spaced equidistantly circumferentially of the forward end-portion of the bore 22 which extends to a face-plate 26 with which the cutter-head is provided at its forward end. The face-plate 26 is removably secured in place by suitably applied screws 27 (see Figs. 2, t and 7 and forms the rearwardly facing forward walls of the guideways The bore 22' has its portion which ex ends from the face-plate 26 rearwardly to a point a short distance rearwardly beyond the forwardly facing walls of the guideways 25 smaller diametrically than the remainder of the bore. in diameter between the forward and diametrically smaller end-portion of the bore and the rearward and diametrically larger end- The bore 22 is shown uniform portion of the bore. The guideways 25 ex tend from the bore 22 to the exterior of the diametrically larger portion of the boreformin a horizontall 1 arran ed slidewa a: d a J which extends endwise of the cutter-head and is en aged by a slide-forming collar on a rod which is arranged within and centrally and extends endwise of the bore. Said rod is shiftable endwise and loosely embraced by the collar 71. which is circular in cross-section, as shown in Fig. 6, and moves endwise of said 'slideway with and during the endwise actuation of. the rod. It will be observed therefore that. the surrounding wall of the bore 22 has its portion which extends from end to end of the range of movement of the collar h substan tially corresponding in internal diameter with the external. diameter of said collar. The cutters D, as will hereinafter more clearly appear, are operatively connected with the rod H in such a manner that the cutters are simultaneously shifted from their outer position shown in Fig. 2 into their inner position shown in Fig. 3, or outwardly from their inner position shown in Fig. 3, according as said rod is actuated into its rearward position shown in Fig. 3 or into its forward position shown in Fig. 2. The rod H extends rearwardl-y and forwardly of the collar h a suitable distance. Said rod terminates at. its forward end in a forwardly tapering or conical head 30 arranged within the forward or diametrically smaller end-portion of the bore 22, as shown in Fig. 2, and the circumferential surface of said tapering portion of the rod f rn s an abutment for the inner ends of the cutters, as shown in Figs. 2, 3 and l. The rod H therefore provided at the inner end of its head 30 with a rearwardly facing annular shoulder 32 extending circumferentiall of the rod. The collar IL is spaced rearwardl'v from he shoulder 32 and provided at its forward end, adjacent the rod H. with a forwardly and inwardly facing sloping annular shoulder 83 which extends circumferentially of the rod and is arranged op posite and of course spaced from the shoulder 32 on the rod. Each cutter D conforms at its inner end to the taper of the head 30 of the rod H and is provided at one side thereof, in its inner end-portion, with a recess (Z arranged diagonally of said side of the cutter and parallel with said taper and extending from the rearwardly facing'edge or surface of the cutter forwardly and inwardly to the forwardly facing edge or surface of the cutter. Said recess (1 is engaged by the correspondingly arranged forvward end-portion 34 of a bar I which extends from said recess rearwardly loosely through a slot 35 formed, as shown in Fig. 5, in the rear end-portion of the surrounding wall of the forward and diametrically smaller end-portion of the bore 22 and from said slot rearwardly into and endwise of a recess 36 formed in and extending longitudinally 0f the collar h. That is, as many bars I as there are cutters D are provided, and as many slots 35 are formed in the surrounding wall of the rear end of the forward and diametrically smaller portion of the bore 22 as there are bars I, and the collar h is provided with as many recesses 36 as there are bars I. The slots 35 are spaced circumferentially of the bore 22, as shown in Fig. 5. The recesses 36 in the collar h are arranged at the outer circumference and spaced circumferentially of the collar. The relative arrangement of the parts is such that each recess 36 in the collar 71. is in line endwise with one of the slots 35. Preferably the recesses 36 extend from the forward extremity to the rear extremity of the collar h. The relative arrangement of the parts is preferably such that each bar I has its forward and cutter-engaging portion 3a spaced somewhat rearwardly from the faceplate 26 in the forward position of the rod H. Each bar I is rendered rigid with the rod H as will hereinafter appear so as to be movable with the rod during endwise movement of the rod. The relative arrangement of the parts is furthermore such that the outwardly facing side wall of the recess (Z in each cutter and opposing longitudinal surface of the forward end-portion 3d of the bar I associated with said cutter are arranged to cooperate in actuating said outter from its outer position into its inner position during the endwise movement of said bar from its forward position into its rearward position, and the inwardly facing side wall of said recess and the oppositely arranged longitudinal surface of said portion of said bar are arranged to cooperate in actuating said cutter from its inner position into its outer position during the endwise actuation of said bar from its rearward position into its forward position. The relative arrangement of each cutter and the associated bar I corresponds with the relative arrangement of each other cutter and associated bar, and as the bars I are actuated endwise simultaneously and corres ondingly during the endwise movement of the rod H the cutters are simultaneously actuated inwardly or outwardly according as said rod is shifted rearwardly or forwardly. Preferably each bar I is provided between the shoulder 32 of the rod H and the sloping shoulder 33 of the collar h with an inwardly projecting flange or member 37 which is snugly interposed between said shoulders, and said flange or projecting member of said bar conforms at its rear end to said sloping shoulder. The rod H is screw-threaded from its rear extremity to the rear extremity of the collar h, and a nut 38 is screwed onto said rod and arranged next the rear end of the collar and extends opposite the rear ends of the bars I, and said nut, during the assemblage of the parts, is manipulated as required to cause said collar to clamp the flanges or members 37 of said bars to the shoulder 32 on the rod. It will be observed therefore that the nut 38 constitutes means arranged to prevent rearward movement of the collar h and bars I independently of the rod H, that the flanges or members 37 of said bars and the shoulder 32 of the rod constitute means arranged to prevent forward movement of said bars and said collar independently of the rod, and that said members 37 of said bars, said collar and the aforesaid nut constitute very efiicient means for preventing movement of said bars rearwardly independently of the rod. The rod H, the collar h and the bars I are therefore so assembled and secured together that said bars and said collar can only move endwise with the rod. Preferably the face-plate 26 is recessed or cut away at its rear side and centrally, as at 39, opposite the forward end face of the head 30 of the rod H. The rearward and externally screw-threaded portion of the rod H engages a correspondingly screw-threaded hole 40 formed in and centrally and extend,- ing endwise of the forward and diametrically larger portion G of the hereinbefore mentioned shaft or rotatable member which is shiftable endwise of the adjacent endportions of the

bores

20 and 22 in the stock and cutter-head. Obviously the mutually engaging screw-threads of said rotatable member and the rod permit rotation of said rotatable member on the rod as will hereinafter appear and form an operative con 'nection between the rod and said rotatable member so far as concerns shifting of th rod endwise with and during endwise movement of said rotatable member independently of the cutter-head, and obviously the rod is actuated endwise in the one direction or the other according as said rotatable member is shifted endwise in the one or the other direction. Means for shifting or adjusting said rotatable rod-actuating member endwise of the cutter-head (see Figs. 2, 8 and 13) preferably comprise the side walls of two grooves or recesses and pins 43 engaging said recesses. The recesse; are formed in the forward and diametrically larger portion G of said rod-actuating threaded into and therefore removable from the cutter-head. The pins 43 are arranged diametrically opposite and in line endwise. The relative arrangement of the parts is such that the pins 43 are in engagement with the rear ends of the recesses 42 when said rod-actuating member and the connected rod H- are in their forward position. The relative arrangement of the parts is furthermore such that during the rotation of said rod-actuating member in the direction indicated by the arrow 44, Fig. 8, the pins 43 and the forwardly facing side walls of the recesses 42 cooperate in shifting said rod-actuating member and connected rod rearwardly, and that when said 1od-actuating member is in its rearward position shown in Fig. 3 the rearwardly facing side walls of said recesses 42 and said pins 43 are arranged to cooperate during rotation of said rod-actuating member in the opposite direction in actuating said rodactuating member and connected rod forwardly from the position shown in Fig. 3 into the position shown in Fig. 2. It will be observed therefore that the forward and diametrically larger portion G of said rodactuating member and the surrounding portion of the cutterhead are provided at the outer circumferential surface of said portion of said rod-actuating member with means whereby said rod-actuating member is caused to move endwise rearwardly or forwardly according as said rod-actuating member is rotated in the one or the other direction. I would here remark that the pitch of the mutually engaging screwthreads of said rod-actuating member and the connected rod is so little compared with the pitch of the inclines formed by the side walls of the recesses 42 that the screwthreaded connection between said rod-actuating member and the connected rod does not interfere with the required endwise movement of the rod during the rotation of said rod-actuatingmember on the rod.

Within the bore :20 in the stock and rearward of the diametrically smaller portion 9 of the rod-actuating member (see 2) is arranged a spiral spring K which extends longitudinally or endwise of the stock between the rear end of said rod-actuating member and the rear end of the stock and is attached at its forward end to said rodactuating member and at its rear end to a plug L which forms a closure for the rear end of said bore and is screw-threaded and screwed into the stock and therefore adjustable to enable placing. of the spring under the desired tension. Ascrew. Z, which (see Figs. 2 and 10) is threaded into and arranged radially of the plug-surrounding rear end-portion of the stock, extends into but is withdrawable from a slot 45 formed in and extending endwise of the plug L, and said screw is instrumental in preventing rotation of the plug. A lock-nut 46 is shown. screwed onto said plug against the rear end of the stock. The spring K not only acts to retain the aforesaid rod-actuat ing member and the connected cutter-head in-their rearward position but acts to rotate said rod-actuating member in the direction indicated by the arrow 44, Fig. 8.

The cutter-head is preferably supported from the stock B through the medium of 'pins bw-hich (see-Figs. 9 and 1 1) are carried by and rigid with the stock and 'extend into the cutter-head which is slidably mounted on said pins. The pins are of course arranged horizontally and parallel with the bores 20 and 2:2 and spaced circumferentially of the diametrically larger and adjacent ends of said bores and the cutter-head abuts normally at its rear end facev against the forward end face of the stock and is movable forwardly on said pins against the action of the spring K. Preferably the cutter-head-supporting pins Z) loosely engage correspondingly arranged holes 48 formed in the cutter-head and extending forwardly from the rear end face of the cutter-heath and obviously said pin (see also Fig. 8) prevent rotation of the cutter head on the aforesaid rodactuating member.

Within the rear portion of the forward and diametrically larger end-portion of the bore 20 in the stock is a ring M (see Figs. 2, 3, 9 and 12), and the surrounding wall of said end-portion of said bore affordsbearing to said ring. The ring M is adjustable circumferentially of the rearward and diametrically smaller portion of the aforesaid i rod-actuating member and arranged concentrically relative to said rod-actuating member. Said rod-actuating member is small enough in diameter in any part thereof rearwardly of the forward and diametrically larger portion G of said rod-actuating member to avoid interference by the ring M with the required range of endwise movement of said rod-actuating member, and the relative arrangement of the parts is such that said forward and diametrically larger portion of said rod-actuating member is spaced far enough forwardly from said mug in the forward position of said rod-actuating member to permit the required rearward endwise movement of said rod-actuating member. The ring M is provided with an external annular recess which extends circumferentially of the ring. Said ring is provided with two pins 51 which are parallel with and spaced circumferentially of the rearward and diametrically smaller portion 9 of the aforesaid rod-actuating member and extend into and transversely of the recess 50 and have their recess-engaging portions forming two Shoulders 52 arranged between the side walls of said recess. It will be observed therefore that the ring M is provided with two shoulders 52 spaced circumferentially of the rearward and diametrically smaller portion 9 of the rod-actuating member, and said shoulders face laterally in the same direction. One of the shoulders 52 is engaged by the inner end of one screw of a pair of parallel screws 53, and the other of said shoulders is engaged by the inner end of the other of the said screws. Said screws engage and extend through correspondingly arranged and correspondingly screw-threaded holes 5st formed in the stock and cooperate with the shoulders 52 in constituting means for securing the ring M in the desired adjustment circumferentially of the adjacent portion of the aforesaid rod-actuating member, and obviously said ring is readjusted circumferentially of said portion of said rod-actuating member by the required manipulation of said screws. By the construction hereinbefore described it will be observed that the screws 53 are threaded into the stock at one side 'of the stockand opposite the shoulders 52 of the ring M and form abutments for said shoulders, and the relative arrangement of the parts is such that the rearwardly facing forward side wall of said recess is arranged in close proximity to said screws and cooperates with said screws in constituting means for preventing forward endwise displacement of said ring. It will also be observed that the forwardly facing end wall 55 of the forward and diametrically larger end-portion of the bore 20 in the stock is arranged to prevent rearward endwise displacement of the ring M. One of the pins 51 has its forward end-portion enlarged diametrically, as at 56, and both of said pins are flush at their forward extremities with the forward end face of the ring M. Said ring is provided at its forward end face with a recess 57, as shown in Fig. 12, and said recess is formed largely in the diametrical enlargement 56 of the pin having said enlargement and forms a shoulder 58 facing in a direction opposite to the direct-ion in which the rod-actuating member is rotated, as will hereinafter more fully appear, for the rearward actuation of said rod-actuating member and connected rod. A recess 60 is formed in. said rod actu t g m m a the which extends endwise of said recess and, in

the rearward position of the cutter-head, extends into the recess 57 in the ring M and abuts at its rear end against the forwardly facing end wall of said recess in said ring, as shown more clearly in Fig. 12, and overlaps the shoulder 58 of said ring and thereby cooperates with said shoulder in looking said rod-actuating member against rotation in the direction indicated by the arrow in Fig. 8. The locking bar P (see Figs. 2 and 8) is provided at the surrounding wall of the rearward and diametrically larger end-portion of the bore 22 in the cutter-head with an outwardly projecting externally screwthreaded stud 62, and a handle 63 for manually rotating the aforesaid rod-actuating member is screwed onto and removable from said stud. Said handle extends through a slot 64 formed in the surrounding wall of the rearward and diametrically larger endportion of the bore 22 in the cutterhead and extending circumferentially of the forward and diametrically larger portion G of the rod-actuating member. The handle 63 extends into close proximity to the side walls of the slot 64: so that the handle, and consequently the locking bar P, can not move forwardly or rearwardly,-that is, endwise,- independently of the cutter-head. The handle 63 is shown extending through a hole 65 formed in an annular shell 66 which loosely surrounds or embraces the stock and is rotatably mounted on the cutter-head next rearward of arearwardly facing annular shoulder 67 which is formed on and externally of the cutter-head and spaced forwardly from the handle 63'which extends outwardly beyond the outer circumferential surface of saidshell. The slot 64: extends such a distance circumferentially of the aforesaid rod-actuating member and the relative arrangement of the parts is such as required to accommodate the location of the handle 63 during rotation of said rod-actuating member. By the construction hereinbefore described it will be observed that the rotatable rodeactuating member, the looking bar P, the handle 63 and the shell 66 are all carried by the cutter-head, that said rodactuating member is movable endwise with and independently of the cutter-head, that the locking bar P is only movable endwise with the cutter-head, and that said locking bar loosely engages the recess 60 in said rodactuating member to permit said rodactuating member to move endwise independently of said bar. -Obviously said rod-actuating iii-ember is rendered free to be rotated in the cutter-head .in the direction indicated by the arrow 44,:Eig. 8, upon the movement f the cutter-head far enough forwardly from the stock to remove or withdraw the looking bar P forwardly from opposite the shoulder 58 of the circumferentially adj ustable ring Min the stock andthereby render the locking means formed by said bar and saldshoulder inoperative and thereby releasing said rod-actuating member subject to theiaction of the spring K. I would here remark that during :the rotationof said rodactuating :member in the direction indicated by :the arrow 44, Fig. 8, by the spring'K, 101 by means :of the handle 63, OrzbYsbOlih :the handle and the spring, :the locking-bar P, although not visible in Fig. becauselof the movement of said rbZtP'itHCl connected handle with said rotation. of said rod.actuating membeiyobviousl-y travels vin contact with the forward end face of the ring M and :remains in contact with said end face of said ring upon said rotation of saidlrod1actuating member until said rod-actuating :member, preparatory to the next succeeding screw-threa'd-cutting operation, has again been rotated through :the medium of .the

ber has come oppositethe recess 57 inthe ring That is,-'during said-rearward movement of thecutter-head against the-stocksa-id locking bar again enters said recess and again overlaps the shoulder 58 asrequired toagain lock said rod-actuating member against :ro-

tation in the direction indicated by the arrow 44:, Fig. 8. I would a:lso;remark-that preferably the cutter-headsurrounding shell 66 extends far enough rearward-1y to embrace the stock during the entire movement of the cutter-head forwardly 'fromthe stock, and hence operates, during saidmovement, as a guard for excluding metal shavings or other matter from the space between the stock and cutter-head in the forward position of the cutter-head.

The outer circumferential surface of the shell 66 is provided adjacent the forward end of the stock (see Fig. 1) with a line or mark 'ZO which cooperates with a scale formed on the adjacent portion of the outer circumferential surface of the stock to indicate the circumferential adjustment of-the ring M and consequently the adjustment or position of the cutters. 7

It will also be observed that 73, in Fig. 1. indicates a lug formed on the bed A and arranged to limit movement of the work- 'feeding 'head f E toward my improved tap 'or sorew-threadcutting device; The rela tive arrangement of the parts is'such that,

whenthework flif' has been fed by said workfeeding head into position to .be' operated on by ithecutters and rotated while being operated on by the cutters the stop 73 will arrest endwise movement of the work-feeding head nearztheendof the operation on the work by the cutters, whereupon the rotating work,

forwardly from the .ringM for thepurpose I vhereinbefore described.

What I claim ;is 1. In a screwsthread-cutting device, th combination, with a cutter-head having guideways arranged substantially radially of. the cutter-head, and cutters engaging said guideways, of a rod arranged within and extending and shiftable endwise of the. cut- -ter hea-d and having its forward end-portion iprovided with a i'earwardly facing shoulder extending circumferentially of the rod, bars arranged longitudinally and. spaced circum-ferentially of' the rod and having flanges -or members clamped to the aforesaid shoulder, means whereby the cutters are actuated inwardly or outwardly according as said bars are nove'd endwise with-the rod in the oneor the other direction, and cream for actuating the rod endwise.

2. In a soreuHthread-cutting device; the combination, with a cutter-head having guideways arranged substantially radially of the -cutter'-head, and cutters engaging said guideways, of an cndwise shiftable rod arranged within and extending endwise of thecutter-head and-having its forward porti'on provided with a rearwardly facing shoulder extending circumferentially of the rod, a collar loosely mounted on the rod rearwardly of and spaced from said shoulder and provided at its forward end with a forwardly and inwardly facing slop ng shoulderextcnding circumferentially of the rod, means for preventing movement of the cellar rearwardly independently of the rod, barsarranged longitudinally and spaced circumferentially of the rod and having members snugly interposed between the aforesaidshoulders,:means whereby the cutt-ers are actuated inwardly or outwardly according as said :bars' are actuated endw-ise with the rod in the one or the other direction, and means for actuating the .rod end- "wise.

3.1. 11 a screw-thread-cutting device, the combination, with a cutter-head having its -=forward portion provided with guideways arranged"substantially radially of the cut terlread, and :cutt-ers engaging said guideways, of an endwise shiftable rod arranged within and extending endwise of the cutterhead and provided at its forward end with a forwardly tapering head having its outer circumferential surface arranged to form an abutment for the inner ends of the cutters, bars arranged longitudinally and spaced circumferentially of the rod and extending into the aforesaid recesses and having members clamped to the aforesaid head, means whereby the cutters are actuated inwardly or outwardly according as said bars are actuated endwise with the rod rear wardly or forwardly, and means for actuating the rod endwise, the cutters being in their outer position in the forward position of the rod.

a. In a screw-thread-cutting device, the combination, with a cutter-head having guideways arranged substantially radially of the cutter-head, and cutters engaging said guideways, of a suitably actuated endwise shiftable rod arranged within and extending endwise of the cutter-head and having its forward end-portion provided with a rearwardly facing shoulder extending circumferentially of the rod, a collar extend ing circumferentially of and loose relative to the rod and spaced rearwardly from said shoulder, a nut screwed onto the red at the rear end of the collar, bars arranged longitudinally and spaced circumferentially of the rod and having members interposed between the collar and the aforesaid shoulder, and means whereby the cutters are actuated inwardly or outwardly according as said bars are actuated endwise with the rod in theone or the other direction.

5. In a screw-thread-cutting device, the combination, with a cutter-head having guideways arranged substantially radially of the cutter-head, and cutters engaging said guideways, of a suitably actuated endwise shiftable rod arranged within and extending endwise of the cutter-head and having its forward end-portion provided with a rearwardly facing shoulder extending circumferentially of the rod, a collar extending circumferentially of and loose relative to said rod and spaced rearwardly from said shoulder, means arranged to prevent movement of the collar rearwardly independently of the rod, bars arranged longitudinally and spaced oircumferentially of the rod "and having members interposed between the collar and the aforesaid shoulder, and means whereby the cutters are actuatedinwardly or outwardly according as said bars are moved endwise with the rod rearwardly or forwardly, the cutter-head being provided internally with a slideway for said collar.

6. In a screw-thread-cutting device; the combination, with a cutter-head having a centrally located bore which extends endwise of the cutter-head and guideways arranged substantially radially of the cutterhead, saidbore being circular in cross-section, of a suitably actuated endwise shiftable rod arranged within and extending endwise of said bore and having its forward end-portion provided with a rearwardly facing shoulder extending circinnferentially of the rod, a collar extending circumferentially of and loose relative to said rod and spaced rearwardly from said shoulder, means arranged to prevent movement of the collar rearwardly independently of the rod, bars arranged longitudinally and spaced circumferentially of the rod and having members interposed between the collar and the aforesaid shoulder, and means whereby the cutters are actuated inwardly or outwardly according as said-bars are moved endwise with the rod rearwardly or forwardly, the surrounding wall of the aforesaid bore having its portion which extends from end to end of the range of movement of the afore said collar endwise with the rod uniform in diameter and forming a slideway for said collar.

7. In a screw-thread-cutting device,.the combination, with a cutter-head having a centrally located bore which extends endwise of the cutter-head and provided in its forward portion with substantially radially arranged guideways, and cutters engaging said guideways, of a suitably actuated endwise shiftable rod arranged centrally of and extending endwise of said bore and having its forward end-portion provided with a rearwardly facing shoulder extending circumferentially of the rod, a collar extending circumferentially of and loose relative to and spaced rearwardly from said shoulder and provided with recesses which are spaced circumferentially of the rod and extend rearwardly from the forward extremity of the collar, a nut screwed onto the rod at the rear end of the collar, bars arranged longitudinally and spaced circumferentially of the rod and having members interposed between the collar and the aforesaid shoulder, and means whereby the cutters are actuated inwardly or outwardly according as said barsare actuated rearwardly or forwardly, said bars engaging the aforesaid recesses.

8. In a screw-thread-cutting device, the combination, with a cutter-head provided in its forward end-portion with substantially radially arranged guideways and having a centrally located bore which extends endwise of the cutter-head and'has its forward end-portion smaller diametrically than the remainder of the bore, and cutters engaging said guideways, said end-portion of said bore having its surrounding wall provided rearward of said guideways with slots spaced circumferentially of the bore, of a suitably actuated endwise shiftable rod arranged centrally and extending endwise of the bore, a collar extending circumferentially of and loose relative to said rod and arranged rear-wardly of the aforesaid slots and provided with recesses each of which is arranged in line endwise with oneof said slots and extends rearwardly from the forward extremity of the collar, means arranged to prevent movement of the collar rearwardly independently of the rod, bars arranged longitudinally and spaced circumferentially of and movable endwise with the rod, and means whereby the cutters are actuated inwardly or outwardly according as said bars are actuated endwise with the rod rearwardlyor forwardly, said bars engaging the aforesaid recesses and the aforesaid slots.

9. In a screw-thread-cutting device, the combination, with a stock, a cutter-head arranged forward of and supported and movable forwardly from the stock and provided in its forward portion with substantially radially arranged gui'deways, and cutters engaging said guideways, of a 1'0- tatable-endwise shiftable member arranged within and endwiseof the rear end-portion of and supported from the cutter-head, means whereby the cutters are actuated inwardly or outwardly according as said rotatable member is shifted endwise in the one or the other direction independently of the cutter-head, means whereby said rotatable member is shifted endwise in the one direction'or the other according as said rotatable member is rotated in the one or the other direction, means for locking said rotatable member in the rearward position of the cutter-head against rotation in the direction required to withdraw the cutters from their Work-engaging position, said locking means being adapted to be rendered inoperative upon the movement of the cuttor-head forwardly from the stock the required extent, and means for rotating said rotatable member upon said movement of the cutter-head.

10. In a screw-thread-cutting device, the combination, with a stock, a cutter-head arranged forward of and movable forwardly from. the stock and having substantially radially arranged guideways, and cutters engaging said gui'deways, of a suitably supported rotatable endwise shiftable member spaced rearwardly from the cutters, :means whereby the cutters are actuated inwardly or outwardly according as said rotatable member is shifted endwise in the one or the other direction, means whereby said rotatable member is shifted endwise in the one direction or the other according as said rotatable memberis rotated in the one or the other direction, means for locking said rotatable member in the rearward position of the. cuttenhead against rotation an the direction required to effect the shifting of the cutters from their outer into their inner position, said locking means being adapted to be rendered inoperative upon the movement of thecutter-head forwardly from'thestock, and means for rotating said rotatable member upon said movement of the cutterhead.

11. In a screw-thread-cutting device, the combination, with a stock, a cutter-head ar ranged forward of and supported and movable forwardly from the stock and provided in its forward portion with substantially radially arranged guideways, and cutters engaging said guideways, of a rotatable endwise shiftalole member arranged within and endwise of the rear end-portion of and supported from the cutter-head, means whereby the cutters are actuated inwardly or outwardly according as said rotatable member is shifted endwise rear-wardly or forwardly independently of the cutter-head, means whereby said rotatable member is shifted endwise rearwardly or forwardly according as said rotatable member is 1'0- tated in the one or the other direction, means for locking said rotatable member in the rearwardposition of the cutter-head against rotation in the direction required to effect the shifting of the cutters from their outer into their inner position, said locking means being adapted to be rendered inoperative upon the movement of the cutter-head forwardly from the stock the required extent, and means for rotating said rotatable member upon said movement of the cutter-head.

12. In a screw thread-cutting device, the combination, with a stock having a centrally arranged bore extending endwise of the stock, a cutter-head arranged forward of and movable forwardly from the stock and having substantially radially arranged guideways, cutters engaging said guideways, a rotatable endwise shiftable member spaced rearwardly from the cutters, means whereby the cutters are actuated inwardly or out wardly according assaid rotatable -member is shifted rearwardly or forwardly independently of the cutter-head, and means for locking said rotatable member against rotation in the direction required to actuate the cutters inwardly, said locking means being adapted to be rendered inoperative upon movement of the cutter-head forwardly from the stock, and means whereby said rotatable member is caused to move rearwardly during rotation of said rotatable member in the aforesaid direction, of a spiral spring arran ed within and longitudinally oft-he a foresaidbore and attached at its forward end to said rotatable member and connected at its rear end to the stock and acting to rotate said rotatable member in said direction.

18. In a screw-thread-cutting device, the combination, with a stock having a centrally arranged bore which extends from end to end of the stock and has its forward endportion larger diametrically than the remainder of the bore, a cutter-head arranged forward of and supported from the stock and having a centrally arranged bore which extends forwardly from the rear extremity of the cutter-head and has its rearward endportion larger diametrically than the remainder of the bore and corresponding diametrically with the adjacent portion of the first-mentioned bore, said cutter-head having guideways arranged substantially radially of the cutter-head and spaced circumferentially of the forward end-portion of the bore in the cutter-head, of a rotatable member arranged within and shiftable endwise of adjacent portions of the cutter-head and stock, means whereby the cutters are actuated inwardly or outwardly according as said rotatable member is shifted endwise rearwa'rdly or forwardly independently of the cutter-head, and means for rotating saidv rotatable member, the cutters being in their outer position in the forward position of said rotatable member.

14. In a screw-thread-cutting device, the combination, with a stock, a'cutter-head arranged forward of and supported from the stock and provided in its forward portion with guideways arranged substantially radially of the cutter-head, and cutters engaging said guideways, of a rotatable member arranged within and supported from and shiftable endwise of the cutter-head, and means whereby the cutters are actuated inwardly or outwardly according as said rotatable member is shifted endwise in the one or the other direction independently of the cutter-head, said rotatable member and the surrounding portion of the cutter-head being provided the one with a recess and the other with a pin engaging said recess, said recess being formed at and arranged diagonally of the outer circumferential surface and extending circumferentially of said r0- tatable member.

15.111 a screw-thread-cutting device, the combination, with a stock, a cutter-head arranged forward of and supported from the stock and provided in its forward portion with guide'ways arranged substantially radially of the cutter-head, and cutters engaging said guideways, of a rotatable member arranged within and supported from and shiftable endwise of the cutter-head, and means whereby the cutters are actuated inwardly or outwardly according as said rotatable member is shifted endwise in the one or the other direction independently of the cutter-head, said rotatable member and the surrounding portion of the cutter-head being provided the one with a recess and the other with a pin engaging said recess, said recess being formed at and arranged diagonally of the outer circumferential surface and extending circumferentially of said rotatable member, and said pin being threaded into and removable from the pin-carrying member. 7

16. In a screw-thread-cutting device, the combination, with a stock, a cutter-head arranged forward of and supported from the stock and provided in its forward portion with guideways arranged substantially radially of the cutter-head, and cutters engaging said guideways, of a rotatable member arranged within and shiftable endwise of adjacent portions of and having bearing in the cutter-head and stock, and means whereby the cutters are actuated inwardly or outwardly according as said rotatable member is shifted endwise in the one or the other direction independently of the cutter-head, said rotatable member and the cutter-head being provided at the outer circumferential surface of said rotatable member with means whereby said rotatable member is caused to move endwise in the one direction or the other according as said rotatable member is rotated in the one or the other direction.

17. In a screw-thread-cutting device, the combination, with a stock having a centrally located bore which extends from end to end of the stock and has its forward-end-portion larger diametrically than the remainder of the bore, a cutter-head arranged forward of and supported from the stock and having a centrally arranged bore which extends forwardly from the rear extremity of the cutter-head and has its rear end-portion larger diametrically than the remainder of the bore and corresponding diametrically with the adjacent portion of the first-mentioned bore, said cutter-head having substantially radially arranged guideways spaced circumferentially of the forward end-portion of the bore in the cutter-head, and cutters engaging said guideways, of a rotatable member arranged within and shiftable endwise of adjacent portions of and having bearing in the cutter-head and stock and having its forward portion larger diametrically than the remainder of said rotatable member. and means whereby the cutters are actuated inwardly or outwardly according as said rotatable member is shifted endwise in the one or the other direction, independently of the cutter-head the forward and diametrically larger portion of said rotatable member and the cutter-head being provided with means whereby said rotatable member is caused to move endwise in the one direction or the Other according as said rotatable member is rotated in the one or the other direction.

18. In a screw-thread-cutting device, the combination, with a stock, a cutter-head arranged forward of and supported from the stock and provided in its forwardportion with substantially radially arranged guideways, and cutters engaging said guideways of v a suitably supported rotatable member arranged within and shiftable endwise of adj acent portions of the cutter-head and stock and having its forward portion larger diametrically than the remainder of said rotatable member, and means whereby the cutters are actuated inwardly or outwardly according as said rotatable member is shifted endwise into its rearward or forward position, said rotatable member and the cutter-heazil being providedat the outer circumferential surface of said rotatable member with. means whereby said rotatable member is caused to move rearwardly or forwardly according said rotatable member is rotated in the one or the other direction.

19. In a screw-thread-cutting device, the combination, with a stock, a cutter-head arranged forward of and supported from the stock and provided in its forward portion with substantially radially arranged guideways, and cutters engaging saidguideways, of a suitably supported rotatable member arranged within and shiftable endwise of adjacent portions of the cutter-head and stock and having its forward portion larger diametrically than the remainder of said rotatable member, and means whereby the cutters are actuated inwardly or outwardly according as said rotatable member is shifted endwise in the one or the other direction, independently of the cutter-head, the diametrically larger portion of said rotatable member and the surrounding portion of the cutter-head being provided the one with two recesses and the other with two,

pinsengaging the difierent recesses respectively, said recesses being formed at and arranged diagonally and extending circumferentially of opposite portions respectively of said rotatable member, and the one side wall or the other side wall of each recess being arranged to cooperate with the pin engaging said recess in shifting said rotatable member endwise in the one directionor the other according as said rotatable member is rotated inthe one or the other direction.

20,. In a. screw-thread-cutting device, the combination, with a stock, a cutter-head ar ranged forward of and supported from the stock and provided in its forward portion with guideways arranged substantially radially of the cutter-head, and cutters engaging said guideways, of a suitably supported rotatable member arranged within and shif able endwise of adj acent, portions of the cutter-head and stock, andmeanswhereloy the cutters are actuated inwardly or out wardly according as said rotatable member is shifted rearwardly or, forwardly, independently of the cutter-head, said rotatable member and the surrounding portion of the cutter-head being provided the one with two diagonally arranged recesses and the other with two pins engaging the different recesses respectively, the cutters being in their outer position in the forward position of said rotatable member and the one or the other side wall of each recess and the pin engaging said recess being arranged to cooperate in actuating said rotatable member rearwardly or forwardly according as said rotatable member is rotated in the one or the other direction.

21 In a screw-thread-cutting device, the combination, with a stock, having a centrally arranged bore extending. from end to end of the'stock, a cutter-head arranged forwardof and supportedcand movable forwardly from the stock and provided in its forward portion with substantially radially arranged guideways, cutters engaging said guidew-ays, a suitably, supported rotatable member arranged within and shiftable endwise of adjacent portions of the cutter-head and stock, means whereby the cutters are actuated inwardly or outwardly according as said rotatable member is shifted rear- Wardly or forwardlyindependently of the cutter-head, and means for locking said rotatable member-against rotation in the direction required to actuate the cutters inwardly, said locking means being adapted to be rendered inoperative upon movement of the cutter-head forwardly from the stock the re quired extent, the cutters being in their outer position in the forward position of said rotatable member, and said rotatable member and the cutter-head being provided with means whereby said rotatable member is caused to move re arwardly during rotation of said rotatable member in the aforesaid direction, of' a spiral spring arranged within and longitudinally of the aforesaid bore and attached at. its forward end to said rotatable memberand connected at its rear end to the stock and acting to rotate said rotatable member in said direction.

22. In a screw-thread-cutting device, the combination, with a stock having a shoulder, acutter-head arranged forward of and movable forwardly from the stock and having substantially radially arranged guideways, cutters engaging said guideways, a rotatable member spaced rearwardly from the cutters and movable endwise with and independently of the cutter-head, means whereby the cutters are actuated inwardly or outwardly according as said rotatable member is shifted endwise in the one or the other direction independently of the cutter-head, and means whereby said rotatable member is actuated to shift the cutters inwardly during rotation of said rotatable member in one direction, 'of a locking bar movable endwise with and during endwise movement of the cutter-head and overlapping the aforesaid shoulder in the rearward position of the cutter-head and being adapted to be removed from opposite said shoulder by and during movement of the cutter-head forwardly from the stock, said shoulder and said bar in the shoulder-over lapping position of the bar being arranged to lock the aforesaid rotatable member against rotation in the aforesaid direction.

23. In a screw-thread-cutting device, the combination, with a stock, having a shoulder, a cutter-head arranged forward of and supported and movable forwardly from the stock and provided in its forward portion with substantially radially arranged guideways, cutters engaging said guideways, a suitably supported rotatable member arranged within and endwise of ad acent portions of the cutter-head and stock and movable endwise with and independently of the cutter-head, means whereby the cutters are actuated inwardly or outwardly according as said rotatable member is shifted rearwardly or forwardly independently of the cutter-head, the cutters being in their outer position in the forward position of said rotatable member, and said rotatable member and the cutter-head being provided with means whereby said rotatable member is caused to move rearwardly during rotation of said rotatable member in one direction, of a locking bar movable endwise only with and during endwise movement of the cutterhead and overlapping the aforesaid shoulder in the rearward position of the cutterhead and being adapted to be removed from opposite said shoulder by and during movement of the cutter-head the required extent forwardly from the stock, said shoulder and said bar in the shoulder-overlapping position of the bar being arranged to lock the aforesaid rotatable member against rotation in the aforesaid direction.

24:. In a screw-thread-cutting device, the combination, with a stock having a shoulder, a cutter-head forward of and supported and movable forwardly from the stock and having substantially radially arranged guideways, cutters engaging said guideways, a rotatable member arranged within and endwise of adjacent portions of the cutterhead and stock and movable endwise with and independently of the cutter-head, means whereby the cutters are actuated inwardly or outwardly according as said rotatable member is shifted rearwardly or forwardly independently of the cutter-head, the cutters being in their outer position in the forward position of said rotatable member, and said rotatable member and the cutterhead being provided with means whereby said rotatable member is caused to move rearwardly during rotation of said rotatable member in one direction, of a locking bar movable endwise only with and during endwise movement of the cutter-head and provided internally of the cutter-head with an outwardly projecting stud and overlapping the aforesaid shoulder in the rearward position of the cutter-head and being adapted to be removed from opposite said shoulder during movement of the cutter-head forwardly from the stock, and a handle screwed onto the aforesaid stud, said shoulder and said bar in the shoulder-overlapping post tion of the bar being arranged to lock the aforesaid rotatable member against rotation in the aforesaid direction, and the cutter-head being slotted to accommodate the location of the aforesaid handle during rotation of said rotatable memberf :25. In a screw-thread-cutting device, the combination, with a stock having a shoulder, a cutter-head arranged forward of and movable forwardly from the stock and provided in its forward portion with substantially radially arranged guideways, cutters engaging said guideways, a rotatable member arranged within and endwise of adjacent portions of the cutter-head and stock and movable endwise with and independently of the cutter-head, and means whereby the cutters are actuated inwardly or outwardly according as said rotatable member is shifted rearwardly or forwardly independently of the cutter-head, the cutters being in their outer position in the forward position of said rotatable member, and said rotatable member and the cutter-head being provided with means whereby said rotatable member is caused to move rearwardly during rotation of said rotatable member in one direction, of a locking bar movable endwise only with and duringendwise movement of the cutterhead and overlapping the aforesaid shoulder in the rearward position of the cutter-head, an annular shell rotatably mounted on adjacent portions of the stock and cutter-head, and a handle secured to the aforesaid bar and extending through and externally of said shell, said bar and the aforesaid shoulder in the shoulder-overlapping position of the bar being arranged to lock the aforesaid rotatable member against rotation in the aforesaid direction, and the cutter-head being slotted to accommodate the location of the aforesaid handle during rotation of said rotatable member.

26. In a screw-thread-cutting device, the

combination, with a stock having a shoulder, a cutter-head arranged forward of and movable forwardly from the stock and provided in its forward portion with substantially radially arranged guideways, cutters engaging said guideways, a rotatable member arranged within and endwise of and movable endwise with and independently of the cutter-head and having a recess extending endwise of said rotatable member, and means whereby the cutters areactuated inwardly or outwardly according as said rotatable member is shifted rearwardly or forwardly independently of the cutter-head, the cutters being, in their outer position in the forward position of said rotatable member, and said rotatable member and the cutter-head being provided with means whereby said rotatable member is caused to move rearx'vardly during rotation of said rotatable member in one direction, of a locking bar engaging. the aforesaid recess and movable endwise only with and duringv endwise movement of the cutterhead and overlapping the aforesaid shoulder in the rearward position of the cutter-head and being adapted to be removed from opposite said shoulder during movement of the cutter-head forwardly fromthe stock, said shoulder and said bar in the shoulder-overlappin position of the bar being arranged to 100 z the aforesaid rotatable member against rotation in the aforesaid direction.

27. In a screwthread-cutting device, the combination, with a stock, a eutter-head arranged forward of and movable forwardly from the stock and having substantially radially arranged guideways, cutters engaging said guideways, a suitably supported rotatable member spaced rearwardly' from the cutters and movable endwise with and independently of the cutter-head and havinv a recess extending endwise of said rotatjble member, means whereby the cutters are actuated inwardly or outwardly according as said rotatable member is shifted endwise in the one or the other direction independently of the cutter-head, and means whereby said rotatable member is actuated to shift the cutters inwardly during rotation of said rotatable member in one direction, of a member extending and adjustable circumferentially of said rotatable member and provided at its forward end with a shoulder. and a locking bar engaging the aforesaid recess and movable endwise with and during endwise movement of the cutter-head and overlapping said shoulder in the rearward position of the cutter-head, said shoulder and said bar in the shoulder-oven lapping position of the bar being arranged to lock the aforesaid rotatable member against rotation in the aforesaid direction.

28. In a screw-thread-cutting device, the combination, with a stock, a cutter-head arranged forward of and movable forwardly from the stock and having substantially radially arranged guideways, cutters engaging said guideways, a rotatable member arranged within and movable endwise with and independently of the cutter-head and having arecess extending endwise of said rotatable member, and means whereby the cutters are actuated inwardly or outwardly according as said rotatable member is shifted rearwardly or forwardly independently of the cutter-head, the cutters being in their outer position in the forward position of said rotatable member, and said rotatable member and'the cutter-head bein provided with means whereby said rotatable member is caused to move rearwardlyduring rotation of said rotatable member in one direction, of a ring having bearing in the stock and extending and adjustable circumferentially of said rotatable member and provided at its forward end with a shoulder, a locking bar engaging the aforesaid recess and movable endwise only with and during endwise movement of the cutter-head and overlapping said shoulder in the rearward position of the cutter-head, and said shoulder and said bar in the shoulder-overlapping position of the bar being arranged to lock the aforesaid rotatable member against rotation in the aforesaid direction.

29. In a screw-thread-cutting device, the combination, with a stock, a cutter-head arranged forward of and movable forwardly from the stock and having substantially radially arranged guideways, cutters engaging said guideways, a rotatable member arranged wlthin and endwise of and movable endwise with and indepei'idently of the cutter-head and having a recess extending endwise of said rotatable member, means whereby the cutters are actuated inwardly or outwardly according as said rotatable member is shifted rearwardly or forwardly independently of the cutter-head, the cutters being in their outer position in the forward position of said rotatable member, and said rotatable member and the cutter-head being provided with means whereby said rotatable member is caused to move rearwardly during rotation of said rotatable member in one direction, of a member having bearing in the stock and extending and adjustable circumferentially of said rotatable member and provided at its forward end face with a recess arranged in registry with the aforesaid recess in said rotatable member in the rearward position of the cutter-head, and a locking bar engaging the first-mentioned recess and movable endwise only with and during endwise movement of the cutter-head and extending into the second-mentioned recess in the rearward position of the cutterhead and being removed from said secondmentioned recess upon movement of the cutter-head the required extent forwardly from the stock.

30. In a screw-thread-cutting device, the

combination, with a stock, a cutter-head arranged forward of and movable forwardly from the stock and having substantially radially arranged guideways, cutters engaging said guideways, a suitably supported rotatable member spaced rearwardly from the cutters and movable endwise with and independently of the cutter-head, means whereby the cutters are actuated inwardly or outwardly according as said rotatable member is shifted endwise in the one or the other direction, and means whereby said rotatable member is actuated to shift the cutters inwardly during rotation of said rotatable member in one direction, of a member extending and adjustable circumferentially of said rotatable member, and means for locking said rotatable member to said adjustable member in the rearward position of the cutter-head, said locking means being adapted to be rendered inoperative by movement of the cutter-head forwardly from the stock.

31. In a screw-thread-cutting device, the combination, with a stock, a cutter-head ar ranged forward of and movable forwardly from the stock and having substantially radially arranged guideways, cutters engaging said guideways, a rotatable member arranged wlthin and endwise of and movable endwise with and independently of the cutter-head, means whereby the cutters are actuated inwardly or outwardly according as said rotatable member is shifted rearwardly or forwardly independently of the cutterhead, the cutters being in their outer posi tion in the forward position of said rotatable member, and said rotatable member and the cutter-head being provided with means whereby said rotatable member is caused to move rearwardly during rotation of said rotatable member in one direction, of a ring extending and adjustable circumferentially of and arranged concentrically relative to said rotatable member, and means for looking said rotatable member to said ring in the rearward position of the cutter-head, said locking means being adapted to be rendered inoperative by the required movement of the cutter-head forwardly from the stock.

In testimony whereof, I sign the foregoing specification, in the presence of two witnesses.

THOMAS SHEHAN.

Witnesses CASPER J. Donna, EMIL W. KRYZ.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, I). (1.