US2377384A - Feed control for automatic screw machines - Google Patents

Description

June 5,1945. A LO AK 2,317,384

FEED CONTROL FOR AUTOMATIC SCREW MACHINES Filed April 17, 1943 6 Sheets-Sheet 1 Filed April 17, 1945 e Sheets-Sheet 2 mndr-ew Slovak; I3 full, M

I Va -m cfilTTopqs June 5, 1945. A. SLOVAK 2,377,384

FEED CONTROL FOR AUTOMATIC SCREW MACHINES Filed April 17, 1943 6 She etS-Sheet 3 f wrrowys Nv E NTOw 04mm) cs/ouak,

Illllllllflllllilli! k mwx mw m my June 5, 1945. A. SLOVAK FEED CONTROL FOR AUTOMATIC SCREW MACHINES Filed April 17, 1943 6 Sheets-Sheet 4 Nvmhrrop I (Andrew Slovak,

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TTO L J June 5, 1945'. A. SLOVAK 2,377,334

FEED CONTROL FOR AUTOMATIC SCREW MACHINES Filed April 1.7, 1945 s Sheets-Sheet 5 04nd 5/ L) //a l 9 I I June 5, 1945.

4 A. SLOVAK FEED CONTROL FOR AUTOMATIC SCREW MACHINES Filed April 17, 1943 6 Sheets-Sheet 6 I lllll II lllll III NVSNTOQ C/ ndrew 6/0 vak,

Patented June 5, 1945 FEED CONTROL FOR AUT'OMATIG SCREW MACHINES Andrew Slovak, Rockford, Ill.

Application April 17, 1943, Serial No. 483,402

12 Claims. (01. 164-38) This invention relates to automatic screw machines and more particularly to those of. the type in which an auxiliary collet is provided to grip the advanced end portion of the stock bar while this end portion is being out off whereby to eliminate the formation of a burr. 3

One object is to provide a machine. of the above character which avoids the necessity of using a cut-ofi piece of stock as the stop for limiting the next advance of the stock bar. 7

Another object is to provide a machine of the above character in which each cut-off workpiece is ejected in a novel manner from the auxiliary collet. vance of the stock bar by means of a stop which is movable into and out of the path of the stock in timed relation to the advance and retraction of the auxiliary collet. I

Still another object is to provide a machine of the above character in which a single member is utilized;' to effect ejection of the cut-off piece of stock and as a stop for limiting the next advance of the stock bar. I v

The invention also resides in the novel method of controlling the work ejection and stock advance. I

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings, in which Figures 1 to 4 are fragmentary views illustrating various steps in one method of practicing the present invention. v

Fig. 5 is a vertical sectional view of the headstock.

Fig. 6 is a similar view of the movablehead or auxiliary collet on the oppositeend of the machine. s

Fig. 7 is a fragmentary section taken along the line 'l-'! of Fig. 6.

Fig. 8 is a perspective View showing the collet drive mechanisms. V

Fig. 9 is a perspective view of the actuators for the collets, the stock stop, and the tools.

Fig. 10 is a fragmentary plan view of the tools and their mountings. Y

Fig. 11 is a fragmentary section taken along the line ll-Il of Fig. 10. I

Fig. 12 is a fragmentary view partly in section showing a modified form of the invention.

Figs. 13 and 14 show steps in the modified method.

While the invention. is susceptible of various modifications and may be practiced in various ways, I have illustrated in the drawings and will cuttin A further object is to controlthe ad-v describe here in detail the preferred embodiment and methods. It is to be understood, however, that I do not intend to limit'the invention by such specific disclosure but aim to cover all modifications and alternative constructions and methods falling within the spirit and scope of the invention as expressed in the appended claims.

The embodiment illustrated in Figs. 1 to 11, involves the use of the usual feed finger H for advancing the stock bar l4 step-by-step, a retractible stock stop Ill for limiting each advance, hollow rotary collets or clamps l2 and I3 for gripping the rotating stock M on opposite sides of a tool I5 which is fed transversely of the work to cut off the advanced end portion l6. One method of practicing the invention comprises applying the collets I2 and [3 to grip the stock on opposite sides of the tool l5 (Fig. l), advancing and retracting the tool (Figs. 1 and 2) to cut off the leading end portion 16 and form a finished workpiece l1, axially advancing the auxiliary collet 13 to carry the piece pastthe stop while continuing to grip the finished workpiece (Fig. 2), moving the stop laterally into the path of the leading end N5 of the stock, releasing the clamp I2, advancing the feed finger I I to feed the leading end of the stock against the stop surface l8, applying the clamp l2 to grip the stock in its new position, withdrawing the stop, re-- leasing the clamp l3 and retracting the same to a position overlapping the advanced end portion of the stock, and finally applying this clamp. By controlling the advance of the stock in this manner, and holding the stock end during cut-ofi, great accuracy is obtained irrespective of the shape of the end on the finished piece. Also, the formed surfaces of the finished workpiece are protected against damage, are cleanly finished and Without burrs, and are kept separated from the chips.

Referring now to Figs, 5 and 8, the stock l4 extends through a guide sleeve 20 supported in a block 2| on the headstock frame 22. Beyond this sleeve, the stock projects into the shank 23 of the feed finger ll .whose spring jaws 24 grip the stock. The feed sleeve 23 is journaled at one end in a bearing 25, the outer race of which is enclosed by a head 26 threaded onto the sleeve 20 and connected by a key 27 to a block 28 slidable parallel to the stock on stationary bars 29 (Fig. 8). The block has a T-slot 30 along which a bolt 3| .is adjustable. This bolt supports a bushing 32 projecting through a slot 33 and pivotally connectedto a lever 34 fulcrumed on afixed pivot 35. The free end of the lever is com nected by a link 36 to a lever 31 pivoted at 38 (Fig. 9) and having a follower roller 39 riding in a slot 40 of a barrel cam 4 I. This cam is fixed on a. sleeve 42, rigid with; the driven member 43 of a one-revolution clutch 44 having its driving member 45 fast on a shaft 46 carrying a gear 41, which meshes with the gear 48 (Fig. 8) and is driven through the medium of a jaw clutch 49 normally engaged. by a spring 50.. Asear 5.I fast on the clutch driver is driven through a gear 52 through the medium of a friction clutch 53 on a shaft 54 belt driven from the main drive motor. 55. The clutches 49 and 53 may be engaged and disengaged by manipulation of handles 53 and 51.

Each time the one-revolution clutch 44 is released in the manner to be described later, the cam 4I makes one revolution and the lever 34 is actuated to retract the block 28- and therefore ways II9 formed on the main frame and spaced from the end of the headstock.

To open and close the collet I3, the outer race of the bearing I2 is engaged by a yoke 83 (Figs. 6 and 8) on a U-shaped member 84 pivoted at 84 on the housing 85. An arm 86 on the member 94 is connected by a link 81 having a slidable connection 89 with a rod 88 which is supported by arms. 9 I. fast ona rockshaft92 on the main frame. The lower end of the link 9! projects through a depending boss 90 on the bottom of the head 85.

The opposite end of the rockshaft 92 carries a the feed finger and then after a short dwell advances the finger through a distance determined by the adjusted position of the, bolt, 31: along the slot Usually this distance will. be, slightly greater than. the overall lengtn'oi the. workpiece.

The main collet I2. (Fig. 5) is. of. ordinary con-- struction comprising spring jaws 55 disposed within a sleeve 3 I and adapted; to be squeezed together to grip. the bar by axial. shifting of. the sleeve during which a tapered surface. 60* thereon acts on an inclined surface 59'. The sleeve BI- is slidable in. a power driven. sleeve GI which issup.-- ported by bearinglfl: in the main frame- It is.

connected through a pin 62 toa ring. 63 inclined.

on one. side as shown at 64. and cooperating with. a similarly inclined end it on a sleeve 6-! to form a groove 65, in which. balls: .6 are located. The sleeve, 9:! is enclosed by. a sleeve 1.1 which carries a ball bearing [2 and is. shifted to the right as viewedin Fig; 5 by: a yoke'i3 (Fi s. 8': and; 9) acting on: the outer bearing. race. In thismovement, a surface. I41 cams the balls. inwardly separating the'parts 63 and 6.1: and the resulting axial movement of the sleeve SI: closes the; collet, as shown. in Fig- 5, to grip the bar. In the reverse movementof. the yoke, that is, to theleft as viewed in Fig. 5, the surface III permits the balls to err-- pand and the spring stress: inthe jaws opens the latter; The yoke 13 is carried by an arm I4 pivoted on arockshaft I5 in the mainmachine frame 2-2: and arranged to be actuated. by a hand lever 80 or by cam actuation of anarm IS. The latter carries a follower It which engages a groove 18 in the; barrel cam 4|; The cam surfaces. of the grooves and I8 are correlated to permit the feed finger it to. be retracted while the collet is closed. This is followed by'opening of the collet while the feed finger is being advanced and finally to. again close the collet.

The parts of the machine thus far described are typical of those commonly used in automatic screw machines for advancing a stock bar step-- by-step. In addition, the auxiliary'collet I3, rotated in synchronism with the main collet, is

operated to gri and support the advanced and of the stock while it is being cut off and then to carry the finished workpiece axially and forwardly ast the stop I0.

As shown, the collet I3 is of the same general construction as the main collet I 2' and like parts are indicated by corresponding primed numbers. Since this collet is to be shifted axially, the bear-- ings II'I' (Fig. 6) of the main spindle sleeve 8'lare supported in a housing 85- which is mounted to slide on the main frame of the machine parallel to the work and collet axes. Herein, the housing has flanges I I3 (Fig. '7) which; slideinsecond pair of arms 93 (Fig. 9) having rollers 94 and- 95 that follow cams 96 and 91 which are fast on a shaft 98 and circumferentially adjustable relative to one another to provide a dwell between the opening and the closing of the collet I3, As the camshaft'M-turns clockwise from the position shown in Fig. 9, the cam 95 opens the collet I3 and after a dwell, the cam 91 rocks the shaft 92 reversely. toclose the. collet.

After the collet I3" has been advanced to the position shown in Fig. 2, the stop 10 is yieldably moved into the path of the stock: bar. As shown (Figs. 9: and 10'), the stop It comprises an arm I9 provided with a hardened side surface I8. on one end. The opposite end is fast on a shaft 69 mounted on the main frame 22' in bearings 82 and I42. Theformerisa thrust bearin which permitsrotation but preventsaxial shifting of the shaft. Also fast on the shaft 69 i an arm I06 which is urged-by a torsion spring I IT in a direction to move the arm I9 into active position in the path of the stock It (see Fig. 9), this position being determined by a set screw I06.

Positively acting means is provided for retracting the stop bar I9 to inactive position. This means includes a link I28 connected at one end to the arm I09 and at the other end to a lever I42 pivoted at I42" and carrying a follower roller which rides against the cam 40. A lobe I44 on the follower has a leading surface which times the retraction of the stop arm and a trailing surface which permits the arm to move to active position under the action of the spring I".

In order that the opening and closing of the collets I I and II, the swingingor the stop I0, and the actuation of the feed finger Il may be synchronized, the camshaft 99 is driven from the feed camshaft 45. This drive includes a pair of spiral gears 99, a shaft I00; worm gearing IIH. a shaft I03, and pickoff gears I04. The camshaft 98 also times the operation'of the one-revolution clutch 44. For this purpose, a cam I01 mounted on the shaft I05 is coupled to the shaft 90 by one tooth jaw clutch I00. A lobe I09 on the cam is arranged toengage a projection III) on a follower arm I I I pivoted on a stationary pin I I-2 and rigid: with an arm I I 3 which willbedepressed each time the lobe I09 passes the projection H0: Such movement of the arm I I3 retracts a pin I I 4 which allows the clutch 44 to engage under the action of a spring I I6. The pin I I4 rides in a cam groove I06 and after nearly one revolution, one cam surface I I5 engages the pin whereupon the driven clutch member 43 is shifted axially to disengage the clutch jaws as the revolution is completed.

To shift the head along the ways H9 and move the auxiliary collet I3 axially back and forth, a cored-out extension I2 2 (Fig. 6) projects from the outer end of the head and a nut I24 thereon threads onto one end of a tube IZ-I which is supported at its other end in a lug I20 depending from the head. 1 Withinthetube-is a compressionspring -I-2I' which acts between a plug I26 and a wall of the main frame 22 and thus tends to shift the head to the right, as viewed in Fig. 6. This movement is limited by engagement of a flange I25 on the tube with collar I28 which bears against pins I29 01'' a yoke I30 fast on a rockshaft I 3|. At its other end, this shaft carries a follower arm I32 (Fig. 9) bearing against the periphery of a cam I33 which is fast on the shaft I and therefore rotates counter-clockwise. The cam is contoured to advance the head 86 against the action of the spring I21 and to the right as viewed in Fig. 6 before the collet I3 has been opened to release the cut-off piece of stock. The extent of this motion is determined by the adjustment of the tube I2I relative to the nut I24.

Each workpiece is ejected from the jaws of the auxiliary collet in the retraction of the latter to the left as viewed in Fig. 6. The piece is thus delivered into the coned end I66 of a tubular magazine I64 sized according to the diameter of the workpieces and supported at one end by the sleeve 6| and at the other end by the spindle 8| to which the magazine is connected by a nut I65 threading onto the outer ends of the magazine and the spindle. The pieces are discharged from the remote end of the tube as illustrated in Fig. 6.

The two collet spindles 8| and 8| are driven in unison and continuously. For this purpose, pickoif gears I34 (Fig. 8) connect the shaft 54 to the shaft I 35 connected in turn through gears I36 to a shaft I31 which drives the spindle 8I through gears I38. The shaft I31 is extended beneath the tool I and within the head 85 has a spline connection I39 with a tubular shaft I40 journaled in the head and connected to the spindle Bl through gears I4I having the same ratio as the gears I38. The connection I39 permits the head to shift axially while the spindle 8| continues to rotate.

In the present instance, the tool I5 effects the final cutting off of the advanced end of the stock to form the workpiece and the major portion of the metal is removed by a form tool I45. These tools are clamped in holders I46 and I41 slidable on ways I48 on a bracket fastened to the end of the headstock housing 22 beneath the collet I2. The tool holders are thus adapted to slide transversely of the stock I4 and perform their cutting functions by entering the stock from opposite sides. The tool holders I46 and I41 are adjustably connected by screws I50 to circular racks I5I and I52 meshing with gear teeth on the upper ends of arms I54 only one of which is shown. These arms are actuated bycams I55 and I56 fast on the shaft I05 and shaped to rapid approach, feed, and rapid return the tools i5 and I45. The arm I54 is fulcrumed at I60 and a roller I62. on its lower end bears against the periphery of the cam I56. The cam I55 acts on the roller I6I on the lever I59 which is also pivoted at I60 and is connected by a link I58 to the other arm.

Operation and retraction of the feed finger II are controlled by cams which are driven through the medium of the clutch 44 so that the cams make one revolution during the cycle. At. the time when the clutch 44 becomes engaged by withdrawal of the pin I I4, the parts will be positioned as shown in Fig. 1, the cut-off tool I5 having just completed its operation. At this time, the collet I2 will clamp the stock bar and the collet I3 will clamp the last cut-off workpiece, both collets rotating in synchronism. In the first part of the cycle, the feed finger II and the cut-off .tool I5 are retracted, and at the same time,.the head advanced, after which the stop I0 is moved into active position by the spring II.1 as shown in Fig. 2. In the latter part of the head motion, the cam 18 operates to open the collet I2 thereby releasing the stock bar. The feed finger then advances, moving the leading end I6 of the stock until the same engages the surface I8 of the stop II). The frictional character of the gripping engagement between the stock and the feed finger permits the latter to overtravel slightly during which time the collet I2 is closed clamping the stock in the position shown in Fig. 3. Simultaneously the collet I3 is opened and the stop I0 is retracted, and then the cam I 33 operates to return the head 85.. The advanced end I6 of the stock constitutes a stop for pushing the line of workpieces through the magazine I64 asshown in Figs. 4 and 6. In the final portion of the revolution of the clutch 44, the collet I3 is closed by the cam 91 thereby gripping the advanced end of the bar which is thus held in readiness'for advance of the tools. The form tool I45 first advances to shape the trailing end of the workpiece next to be formed as wellas the leading end of the succeeding workpiece.

For different kinds of workpieces such, for example, as the piece I10 shown 'in Fig. 12 having end portions of different diameters, it becomes necessary to provide for ejection of the finished piece from the auxiliary collet I3 ina different manner and preferably during the advance of this collet which, as described above, follows the cutting off of the piece. Such a modification of the apparatus and method above described is disclosed in Figs. 12, 13, and 14, the parts in common with the apparatus first described bearing corresponding reference numbers. The collet I3 is, of course, shaped according to the contour of the advance end of the workpiece I10 so as to grip and hold this end as shown in Fig. 12 when the collet is closed.

To eject the workpiece, a rod I1I is disposed within the spindle sleeve 8| and is axially slidable in bearings I12 supported thereby. One end of the rod projects beyond the spindle sleeve and is threaded to receive nuts I14 which act as an abutment for a spring I15, the other end of which engages a cap I16 screwed on to the sleeve. The rod is thus urged to the right as viewed in Fig. 12 to a position determined by engagement of its pointed end I13 with an axially adjustable stop I18 screw threaded into the machine frame. Thus, the other rod end I11 which is disposed within the collet jaws is disposed in an accurately defined position in which it acts as a stop for engaging the end of the stock bar I4 to limit the advance of the latter for the succeeding operation.

The cycle of operation of this form of the invention is as follows, it being assumed that the tools I5 and I45 have completed their operation and are retracted. The cam 96 then operates to release the collet-I23 whereupon the. head 85 and the collet. N are shifted to the right from the position. shown in Fig; 13, In this: movement, the end of the rods I'M acts on the workpiece to eiectitvtromcthe collet 1:1. and; to the left whereupon. the finished piece drops down between the two collects, the. collet Iii dwelling in the position showninFlg. 13 in. which the: stop-surface it]; is exposed; At thiatime, the collet It released andthe-feed finger lit is moved forwardly to. advance the stock bar l4 until the leading; end l6 engages therstop H11 35. showninlFig. 14. Thereupon thecollet. I Z clamps the bar. and thereleased collet It; is retracted to. a position overlapping the bar end Closing otthe eollet l13:and\ mtting oi oi the workpiece then. proceed as described above; a

I claim. as my invention:

1:. In a machine or; the character described, the combination ofv mechanism for advancing a stock bar step by step and cutting off the advanced and successively, a. rotary collet adapted toclamp and. releasethe leading end of the stock bar and to. rotate. therewith, said collet having an axial recession supporting a succession of. finished: workpieces in end to end: relation; means supporting said collet. for: movement axially of the bar between a. first position. overlapping said leading end and a second position spaced from this end, mechanismv operable to shift sa collet to; said second position; after a piece of said bar has been cutoff, to. release the collet while the finished workpiece, remains supported therein, and then to retract the collet and the supportedwcrkpiece to, said first position after the. next advance of the bar, a stop movable laterally into and outaot the: path of said stock bar and operable, when disposed in saidlpath', to limit the ad Vance of: the stock; and means operabl automatically tomove said stop into active position after advanceof; saidcollet to .said second position and thenretract the stop after advanceof said bar.

2., Imamachine-of the character described, the combination of mechanismior advancing: a stock bar stepv by step and cuttin off theadvanced end successively; a; rotary collet adaptedto clamp and release. the leading; endofi the; stock. bar and to rotate therewith-,. means supporting said collet formovement axially-of the bar between a first position overlappin said leading end and a secnd;- position spaced from. the bar end in the direction of, advance of the bar; mechanism operable to shift said collet, to. said second position after a piece of said bar has been cut ofiito release the collet with said piece supportedatherein, and thenreturn thev collet and the supported pieceto said first-position afterthet'next advance of the bar, a, stop. member movable transversely ofthe-path of the stock bar and collet, andrmeans. for moving said member into said path while; the shiftable collet isinlsaidsecondmositicn and out of, the path, after the advance of said stock bar and before the return of said collet to said first mentioned position.

3. In a machine of the character described, the combination oi mechanism ior advancing, a, stock bar step by step and cutting? off: the advanced end successively, a rotary collet adapted to:-c1ampand release the leading end of the stock bar and to rotate therewith, means supporting said collet for axial movement away from and back toward the advanced; end of saidstock bar; mechanismfor: opening: said: collet in-v the: advanced: positionof the latter while leaving the previously fin lshed piece supported therein; srmovable stop our limiting the advance of the. st'ocirbar mechanim operable while said; collet ismovedneway from the end oi said her to project said stop into active position to limit theinextadvanoeofi said bar-and than; to; withdraw the stop, and mechanism to retract the open. collet and the. workpiece sup-- ported therein pastthe advancedend of. the bar whereby to: cause the; latter to push the piece throughthe collet,

4. In a machine oi the character described, the combination; on mechani'smfor advancing, a stock per step by-step and cutting of! the advanced end succemively, a rotary collet adapted to: clamp and. release the. leading end of the stock bar and to rotate therewith, means supporting said collet for axial movementaway from and bacic toward: the advanced. end or said; stock bar, mechanism for releasing the collet as an incident toits. advance while retaining the cut-oft. piece supported inthe collet, and a: stop operable while said collet is moved away from the end of said bar to limit: the next advance-of. the bar, the endof the stock bar after such advance operating: during retraction; of said collet to'eject the piece therefrom.

5. In a machine of the character: described, the combination. of mechanism for advancing a stock bar step! by stepand cutting on the advanced and successively,,,a rotary collet adapted to clamp] and release the leading end of; the. stock bar-and to rotate therewith; means: supporting said collet for movement, forwardly to carry the cut-oi! piece away-from the bar and then backwardlyto aposition. overlapping the; advanced end portion of the bar, means operable. automatically aiter cutting off; of the end portion ot the bar to release said co1let,, and. stop-means engageablewith one end, of said cut-oft piece (hiring one of said axial movements of said collet while. released and operating to utilize such movement to shift the piece; axially relative to the: collet and thereby ejectthe. same! from: thecollet.

61., Inzamachlnerofthe character described, the combination of mechanism: for advancing astock bar'step by stern and ofif theadvanced end successively,v a rotary collet adapted to clamp and release theleading end of the stock bar and to rotate therewith,.means supporting said collet for movement forwardly to a carry the cutof! piece away from; the bar and; then backwardly'to a position, overlapping the advanced; endportion of the bar, and: stop; means engageable with one end oi the cut-off piece-during one of said axial movements of: the collet; and utilizing suchmovement to. shift the piece axially relative to the collet and; out, of gripping engagement therewith.

'Z'.v Ina. machine of the character described, the, combination of mechanism for advancing a. stock bar step' by step and cutting on the advanced end successively; a rotary collet. adapted to, clamp. and release' the leading end; of thestock bar and; to rotate therewith, means supporting said collet for movement axially of the bar be,- tween a first position overlapping said leading end and a second position spaced from this end, mechanism operableto' shift said collet to said second position after apiece of said bar has been cut off and to said fi rst position after the next advance of thebar, and a, stopdisposed within said collet inposition to be engaged by the leading endor the stock bar in-thenext advance thereof, said: stopacting' during theaadvence of said collet to said second position; to eject the cut-off piece reversely from the collet and thereby expose the stopfor engagement by the end ofsaid bar.

8. In a machine of the character described, the combination of mechanism for advancing a stock bar step by step and cutting off the advanced end successively, a rotary collet adapted to clamp and release the leading end of the stock bar and to rotate therewith, means supporting said collet for movement axially of the bar between a first position overlapping said leading .end and a second position spaced from the bar in the direction of advance thereof, mechanism operable to shift said collet to said second position after a piece of said bar has been cut oif and to said first position after the next advance of the bar, and a stationary stop member disposed within said shiftable collet along the axis thereof and operable to eject the cut-oil piece reversely from the collet as the latter is moved to said second position, the end of said member being exposed as an incident to such ejection of the cut-ofi piece and thereafter acting as a stop for limiting the advance of the stock bar.

9. The method of controlling the advance of a bar of stock which comprises applying a gripping means to the end portion of said bar, cutting off the bar adjacent said gripping means, advancing the gripping means to separate the cut-off piece from said bar, inserting a stop between said outoif piece and the end of the bar, advancing the bar against said stop, withdrawing the stop, releasing the gripping means, and retracting the gripping means past the advanced end of the bar to carry the cut-01f piece against the bar end and thereby eject the piece through the grippin means.

10. In a machine of the character described, the combination of mechanism for advancing a stock bar step by step and cutting off the advanced end successively, a rotary collet adapted to clamp and release the leading end of the stock bar and to rotate therewith, means supporting said collet for axial movement away from and back toward the advanced end of said stock bar, and a stationary stop for limiting the advance of the stock bar, said stop being disposed on the axis of said collet and operable during the advance of the latter to eject a cut-off piece out of the collet.

11. The method of controlling the advance of a bar of stock which comprises applying a gripping means to the end portion of said bar, cutting off the bar adjacent said gripping means, releasing the gripping means, advancing the gripping means to carry the cut-off piece against a positive stop and then cause ejection of the piece reversely as the advance is continued, advancing the bar against said stop, and retracting the gripping means over the advanced end portion of the bar.

12. In a machine of the character described, the combination of mechanism for advancing a stock bar step by step and cutting off the advanced end successively, a rotary collet adapted to clamp and release the leading end of the stock bar and to rotate therewith, means supDQrting said collet for movement axially of the bar between a first position overlapping said leading end and a second position spaced from the bar in the direction of advance thereof, mechanism operable to shift said collet to said second position after a piece of said bar has been cut off and to said first position after the next advance of the bar, and a member positioned to engage the cut-01f piece during the advance of said collet whereby to eject the piece reversely out of the collet and then to provide an abutment engageable with the leading end of the bar in the succeeding advance thereof whereby to limit such advance.

ANDREW SLOVAK.

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