US2901815A - Apparatus for rifling gun barrels - Google Patents

Description

H. H. $EFR1ED 1| APPARATUS FOR RIFLING GUN BARRELS sept. 1, 1959 INVENTOR.

off/g grill/15115 r .f vf/fill Filed May 2, 1958 Sept. 1, 1959 H. H. sEFRll-:D u

APPARATUS FOR RIFLING GUN BARRELS 2 Sheets-Sheet 2 Filed May 2, 1958 mits advance of the push rod at best at a United States Patent ffice Meme,

2,901,815' APPARATUS Fon RIFLING GUN BARRELS Harry H. Sefried II, New Haven, Conn. Application May z, 195s, serial No. 732,520 13 Claims. (c1. 29-1.1)

This invention relates generally to apparatus for ren forming the wall of a bore through elongated metal stock, and more especially, though not exclusively, to apparatus for riti-ing the bore of a gun barrel.

The most commonly used methods of rilling gun barrels involve either machining, usually breach-ing, of the barrel bores, or displacement of the metal thereof which is commonly calling swaging. This is achieved in either case by forcing a rifling tool or bit through the barrel bore, customarily by means of a separate push rod so that the bit will at the end of its forward passage through the barrel bore drop from the latter whereupon the push rod may be retracted rearwardly from `the 'barrel bore. In either case, the bit encounters quite considerable thrust on its forced passage through the barrel bore, and this thrust is transmitted to the push rod. In View of the fact that the bore diameter is in any event only a small fraction of the length of the barrel, and the push rod not only must have at least non-binding clearance from the barrel bore `but must also be longer than the latter, it stands to reason that the characteristically long and slender push rod will display spring characteristics, presently resilient exing, on being subjected to the considerable end thrust from the `advancing bit in lthe barrel bore. While resilient flexure of the push rod from this cause is largely suppressed and rendered harmless in the barrel bore by virtue of the relatively close guidance afforded by the latter to the push rod, it is the resilient ilexure of the exposed length of the push rod outside the barrel bore, and even of its entire length at the beginning of a riing operation, which would cause hopeless permanent bending, if not breaking, of the push rod if its exposed length were not guided at least to the extent of its guidance in the barrel bore.

To the end of guiding the exposed length of the push rod, recourse has in the past been had to various expediencies. Among these prior expediencies is the one disclosed in the patent to Sampson, No. 2,641,822, dated June 16, 1953. Thus, Sampson uses a series of crossheads which guide the push rod outside a gun barrel to-be-ried and of which the one nearest the `barrel is fixed while the remaining ones are guided on a common track for movement axially of the barrel, with the crossheads having suitable lost-motion connections with each other and with a power ram for the push rod so that the crossheads will successively be moved into butting relation and into equally spaced relation with each other on the advance of the push rod into and on its retraction from the barrel bore, respectively.

While Sampsons guide arrangement of .the push rod is satisfactory and even advantageous over other guide arrangements in some respects, it has been found deticient in at least one vital respect. Thus, it has been found that Sampsons guide arrangement of the push rod, in order yto perform at all, not only requires constant and `close supervision of its performance but permoderate speed Whichl is Well below theV permissible speedgat which the bit may be forced through a barrel bore for satisfactory riiling of the latter. Yet, despite even close and constant supervision of the performance of the guide arrangement and advance of the push rod at the moderate speed indicated, it happens occasionally that a crosshead will suddenly cock and bind more or less severely on the common track yaccompanied by more or less severe binding of the push rod on the respective crosshead, with the result that the ensuing chattering and vibration of the crosshead and ensuing jerky advance, if not breakage, of the push rod will spoil the rifling and, hence, the entire barrel.

It lis the primary 'aim and object of lthe presen-t invention to provide for the push rod in barrel rilling apparatus a guide arrangement which overcomes the aforementioned and also lesser deficiencies of the prior Sampson guide arrangement, while retaining the obvious advantages of a series of rod guides land their lost-motion connections with each other `and with the power ram for the push rod.

Thus, it is among the objects of the present invention to provide for the push rod in barrel ritling apparatus a guide "arrangement which is characterized by a series of rod guides with appropriate lost-motion connections vwith each -other and with the power ram for the push rod, and which permits `advance of the push rod at a speed which is at least equal to the maximum pernn'ssible advance speed of a i'ifling bit in a barrel bore, Without giving rise to any binding or jerky advance of the push rod and, hence, without requiring any supervision of the performance of the rod guides during a riding operation.

It is another object of the present invention to arrange for dual axial guidance of each of the aforementioned movable rod guides by providing a common track for these guides and additionally providing for their guidance on each other in a manner which will obviate any appreciable cocking of any rod guide and, hence, binding of the same on the common track, regardless of the magnitude of Eany twisting yor cooking force from the push rod and despite even more than 'ordinary Wear of the guiding surfaces.

It is a further object of the present invention to space the aforementioned dual guide provisions for each rod guide axially from each other to an extent sulcient to obviate any appreciable cocking of any rod guide under the aforementioned conditions.

Another object of the present invention is to space the dual guide provisions for each rod guide axially from each other to the aforementioned extent, and at the same time considerably reduce the distance between sucl cessive rod guides in their fully spaced relation from the minimum permissible distance which the same number of rod guides would have to be spaced apart if they were guided on a `common ytrack only, thereby not only achieving a significant reduction in the size or length of the apparatus but, even more importantly, affording positive guidance to the exposed length of the push rod at optimum close intervals.

'Other objects and advantages will lappear to those skilled in the art from the following, considered in conjunction with the accompanying drawings.

. In the accompanying drawings, in which certain modes of carrying out the present invention are shown for illustrative purposes:

Fig. 1 is a part-elevational broken longitudinal section through apparatus embodying the present invention;

Fig. 2 is a cross section -through the apparatus taken on the line 2 2 of Fig. l; and

Fig. 3 is a part-elevational 'section similar to Fig. 1, but showing the apparatus at a ditferent stage of its op- A eration. t

Referring to the drawings, the reference numeral designates, in the present example, apparatus for rifling a gun barrel B. The apparatus comprises a bed 12, a barrel. support 14, a push rod 16 for a riing bit 18, a power ram 20 for the push-rod, and guide provisions 2,2' for/the push rod.

The barrel support 14 presently comprises anend'bearing.24,andV au opposite end bearing plate or memberv 26 whichtis removably carried by a fixed bracket 28 onthe bed 12. The end bearing 24 is in the form of a sleeve inwhich the. barrelB is slidably received with one end, and which is presently bolted at 30. in a fixed bracket 32 on thebed 12. The endV bearingmember 26 ispresent- 1y inthe form of a disc having an annular recessfor. seat 34 for the reception of the other end of the barrel'B, and anaperture 36 for the. passage of the pushrod 16 and/or theeriflingbit 18. The bearing member 26. is. further machined yat 38 for removable reception on a preferably frusto-conical seat 4t. at the adjacent end of anaperture 42 in the ixed bracket 28.

The support 14 is adapted releasably to hold aV barrel in place for a riing operation. To this end, a barrel is passed with clearance through the aperture 42. in the bracket 28V and guided into the end bearingy 24, the bearing member 26 being at that time removed from the bracket 28. The end bearing 28 is of adequate length to permit inward sliding of the adjacent end of the barrel until the other end of the barrel is sufficiently spaced from the adjacent bracket 28 to permit the replacement of the bearing member 26 therebetween and also against its seat 4G in the bracket 28, whereupon the barrel is retracted against the seated bearing member and-itself seatedl in the recess 34 therein so as to be held in axial Aalignment with the end bearing 24. Conversely, for removing the barrel from the support 14 it is merely necessary to slide the former deeper into the end bearing 24 to remove it from its seat 34 in the bearing member 261 4and permit removal of the latter from its seat 4i) in the bracket 28.

The push rod 16 is of a cross-sectional size tobe slidably receivable in the bore b of the supported barrel. B,` and is adapted to force or push the rifling bit 18-through the barrel bore for a rifling operation. The bit 18,which may be `entirely conventional and either ofthe aforementioned broaching or swaging type, has the customary riing formations 44, =a pilot shank 46 and an end shank `48mV preferably concavo-convex butting engagement withv the leading end of the push rod 16.

The ram 2t), which is suitably power-operated and adapted to advance the push=rod 16into and substantiallythrough: the bore b ofthe supported barrel B' for the forced passage of the bit 18 therethrough, is axially slidable in a fixed guide bracket 50 onthe bed 12; The trailing end of the push rod 16, which may merely be in butting engagement with the ram 20 forits `advance thereby, is preferably operatively connected with theram. More particularly, the trailing end of thepushtrod 16.is, in the present example, operativelyconnected. at 52 vwith a spring-loaded `head 54 at the forward end ofthe ram 20 for a purpose described hereinafter. Thus, thehead 54 is slidably received in a central recess 56 in the-forward end of the ram 20, and is by an interposed preloaded spring 68 normally urged into a foremost position in which a cross pin 60 in the head engages the end 62 of an elongated slot 64 in the ram. The pin 6()V and. slot 64 in the head 54 and ram 26 constitute a lost-motion connection between the latter.

Since the diameter of the barrel bore b is in. any event only a small fraction of its length, and since the Ybit=18 will on its forced passage throughthebarrel borel encounter quite considerable thrust which is directly trainsmitted to the push rod 16, it stands to reasonthatthe relatively long and slender push rodiwould, over its? entire length at the beginning ofa rilling operationfand over a progressively diminishing length thereof during` a riing operation, be prohibitively flexed resiliently, and may even break apart quite readily, were it not for the guide provisions 22 therefor. These guide provisions 22 serve to keep resilient ilexing of the exposed length of the push rod, either its full length or `any part thereof, at a permissible minimum, if not to prevent altogether any noticeable resilient flexing of the push rod, when the same transmits theA forward motion of the ram 20 to the bit 18 for its forced passage through the barrel bore.

The guide provisions 22 for the push yrod 16 comprise a series of tandem-arranged guide` members 66 which are interposed between the fixed barrel bearing 24 and the ram 20. In laccordance with one aspect of the present invention, these guide members 66 are arranged to telescope with each other, and are to this end provided with telescoping skirts 68, conveniently of circular cross section (see also Fig. 2). The guide members 66 are at one end of their skirts `68, presently in bottom walls 70 thereof, provided vwith central guide apertures 72 for the push rod 16. These guide apertures 72 are present-v ly provided in bushings 74 in the bottom walls 70 ofthe respective guide members 66.

The guide members 66 have also axial lost-motionconnections with each other and with the fixed barrel bearing v24 for their telescopic extension from the latter over a certain distance (Fig. l) and for their telescopicV contraction in each other and into close proximity to the barrel bearing Z4 (Fig. 3). To this end, each of the guide members 66 has, presently in its skirt 68a longitudinal groove 76 into which projects the pin endV 78 of a screw 80 in the adjacent guide member with the next larger skirt, the groove 7 6a in the guide end member 66a next to the barrel bearing 24v-and with the presently largest skirt 68a receiving the pin end 78a of a screw 80a in a lixed tubular track 82 to-be-described which at 84 and 85 is -bolted to a ange 86 on the barrel bearing 24 and to the ram guide bracket 50, respectively.

Besidestelescoping the guide members` 66 as aforementioned, it is another aspect of the present invention to provide for dual guidance of each guide member axially of the barrel bore for the purpose of preventing any guide. member from giving wayl to inevitable twisting or cocking forces from the pushrod 16 when forcing the bit 18 through the barrel bore. Singular or initial guidance of each guide member 66 axially of the barrel bore is alforded by the described telescopic engagement of its skirt 68: with the next larger skirt of the adjacent guide member and by the sliding fit in the aforementioned tubular track 82 of the presently entire length of the largest skirt 68a of the guide end member 66a. It is this tubular track 82 which also affords the additional guidance to the guide members 66 axially of the barrel bore. However, it is in accordance with another important aspect ofthe; present invention that each of these guide members be. additionally guided remotely from its initial guidance in the adjacent guide member with which it telescopes. To this end, each of these guide members.V except the guide end` member 66a, is at the end of its skirt 68 opposite to its .bottom Wall 70 provided with an outward flange 881 which is received with a sliding t in the tubular track 82.

Tor demonstrate the significant `advantage of the described dual guidance of the guide members 66 axially of the barrel bore, let it be assumed that the push rod 16, in forcing the bit 18 through the-barrel bore b, exerts a twisting or cooking couple of even exceptional magnitude tothe guide member 66h (Fig. l), for example, it becomes immediately apparent that thelatter willV not re-V spond to this twisting couple by way of becoming cockedl in the tubular track.82, bnt will respond to. it primarily' by one-sided pressure of its outer ange 88b against the tubulary track 82.l Since the reactive couple in theguidel member 66b is` equal `to thetwisting couple to whichit is, subjectedbythe push rod, and since the reactivecoue ple has the long lever arm I, it stands to reason that the side pressure of the outer flange @8b against the tubular track 82 is very small, and in any event much too small to give rise to the slightest binding of this guide member to the track 82. Hence, regardless of the magnitude of the twisting couple imparted by the push rod 16 to any guide member 66, the latter will never become bound to the track 82 in the slightest, neither will it ever become twisted or cocked in the track 82 to bind the push rod and possibly cause it to break apart.

It follows from the preceding that the present guide provisions for the push rod 16 will never give rise to appreciable resilient flexing of the push rod or to its binding to any of the guide members. This is even true if any or all guide members 66 should have considerable wear and, hence, a relatively loose t in the track 82, for the normal twisting forces transmitted by the performing push rod to the guide members will even then fail to cock the latter in the track to any appreciable extent. Hence, as long as the exposed length of the push rod outside the barrel bore is guided at sufficiently close intervals to keep resilient liexing of the intervening non-guided rod lengths at a permissible minimum, the apparatus may reliably rifle barrels without requiring supervision of its performance and at a speed in excess of the maximum permissible speed of prior `apparatus of this general type. Also, in view of the non-binding feature of the present rod guide provisions, the speed of performance of the apparatus, i.e., the rate of advance of the push rod and bit in the barrel bore, may be made to suit by selecting the proper number of guides 66.

While the ram 20 may be in mere butting engagement with the nearest guide end member 66o so as to require spring or other means for the extension of the guide members 66, it is preferable to have the ram 2t) perform both, the extension and contraction of the guide members 66. To this end, the ram 20 is operatively connected with the nearest guide end member 66e, presently through intermediation of the ram head 54. Preferably, the operative connection between the ram head 54 and guide end member 66e is a lost-motion connection to obtain the full rod-guiding effect of this guide end member 66C as well as have the ram head S4 itself perform the additional function of a rod guide. To this end, the ram head 54 is slidably received in the skirt 68C of the adjacent guide end member 66C, and their lost-motion connection is in the form of a peripheral groove 90 in the ram head 54 and a disc 92 which is bolted at 94 to the outer llange 88e of the guide end member 66C and has an aperture 96 in which the peripherally grooved length of the ram head is received with a loose sliding it.

Assuming now that a barrel B has just been placed in the support 14 in the aforementioned manner and the ram 20 is in its fully retracted position shown in Fig. 1, it follows that in placing the barrel B, with the bit 18 in place for a rifling operation, in the support 14 the barrel will, through intermediation of the bit 18 and push rod 16, depress the spring-loaded ram head 54 so that the latter will thereafter hold the barrel in rm seating engagement with the recess 34 in the seated bearing member 26 on the bracket 28 until the rifling operation begins. On the subsequent advance of the ram 2li from its retracted position (Fig. 1), the preloaded spring 58 between the ram and its head 54 will ordinarily not overcome the thrust encountered by the bit 18 in the barrel bore b, with the result that the ram head 54 will first become seated on the bottom of the recess 56 in the ram (Fig. 3). The ram head 54 will thereupon advance with the ram 20 and start the advance of the push rod 16, and hence, the advance of the bit 18 in the barrel bore for a riliing operation. Ordinarily, the ram head 54 will advance in the skirt 68e of the associated guide end member 66C until butting the bottom wall 742e thereof, whereupon the ram head 54 and guide end member 66C will advance in unison until the bottom wall 70C of the latter comes into butting engagement with the bottom wall of the next guide member which will then join the unitary advance of the ram head 54 and guide end member 66C. On continued advance of the ram Ztl, the remaining guide members will successively join the already advancing guide members. Thus, in the exemplary stage of a riliing operation shown in Fig. 3, the bit 18 is still some distance away from the discharge end of the barrel bore b and its drop therefrom into the recess 42 in the bracket 2S, while all the guide members 66 are fully telescoped, except the foremost guide end member 66a and the guide member next thereto. By the time the bit 18 leaves the barrel bore b, all the guide members 66 will be fully telescoped and the foremost guide member 66a will also have been advanced into closer proximity to the end flange 86 on the barrel bearing 24. On subsequent retraction of the ram 20, the spring 58 between the ram and its head 54 will first be permitted to take up the lost motion between them, whereupon the lost motion between the ram head and the associated guide end member 66C will ordinarily be taken up before the latter will be retracted. Thereupon, and on continued retraction of the ram 26, the remaining guide members 66 will ordinarily successively be retracted in the same order in which they were advanced, as will be readily understood.

While in the present apparatus the exemplary bit i8 is adapted for rifling a gun barrel, all the advantages of the present rod guide provisions will be secured if another bit is used, for example, for sizing the bore of a gun barrel, in which case the bit encounters similar thrust in the barrel bore on its forced passage therethrough. It is for this reason that the bit is inthe appended claims referred to appropriately as a thrust bit. Also, the apparatus may perform advantageously a bit operation on a relatively small and long bore in elongated stock .generally and not only in a gun barrel. Moreover, while a single push rod is presently guided in the bottom walls of the telescoping skirts of the guide members, it is also `fully within the purview of the present invention to use the same guide members for simultaneously guiding more than one push rod for performing simultaneous bit operations on the bores of more than one piece of elongated stock, by guiding the push rods in the outer ilanges of the guide members. Finally, the common track for the guide members need not necessarily be tubular, but may be in` the form of guide bars, for instance, on which the guide members may be slidably supported with their outer tlanges.

The invention may be carried `out in other specific ways than those herei-n set forth without departing from the spirit and essential characteristics of the invention, and the present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.

What is claimed is:

l. In apparatus for reforming with a thrust bit a longitudinal bore through elongated stock, the combination with a device for releasably holding the stock, a push rod slidably receivable, with its leading end foremost, in the stock bore, and a ram device at the trailing end of the push rod, with said devices being relatively movable axially of the bore in the held stock, of a series of guid members between said devices, said guide members being telescoped axially of the stock bore and having lostmotion connections with each other, and each guide member having an aperture for guiding the push rod axially of the stock bore, and track means supporting the guide members for movement axially of the stock bore, the push rod being of suicient length to be movable, on relative movement between said devices, into and at least substantially through the stock bore for the forced passage of the bit through the latter.

2. In apparatus for reforming with a thrust bit a longitudinal bore through elongated stock, the combination with a device for releasably holding the stock, a push rod for the bit slidably receivable, with its leading end foremost, in the stock bore; and a ram at the trailing end of the push rod and movable axially of the bore in the held stock, of a series of guide members between said device and ram, said guide members being telescoped axially of the stock bore and having axial lost-motion connections with each other, with the guide member nearest said ram being in the path of fous/ard movement of the latter and each yguide member having an aperture for guiding the push rod axially of the stock bore, and track means supporting the guide members for movement axially of the stock bore, the push rod being of suicient length to be movable by said ram into and at least substantially through the stock bore for the forced passage of the bit through the latter.

3. In apparatus for reforming with a thrust bit a longitudinal bore through elongated stock, the combination with a device for releasably holding the stock, a push rod for the bit slidably receivable, with its leading end foremost, in the stock bore, and a ram operatively connected with the trailing end of the push rod and movable xially of the bore in the held stock, of a series of guide members between said device and ram, said guide members being telescoped with each other axially of the stock bore and having axial lost-motion connections with each other, with the guide member nearest said ram being operatively connected with the latter and at leastv each o-f the remaining `guide members having an aperture for `guiding the push rod axially track means supporti-ng the guide members for movement axially of the stock bore, the push rod being of sufficient length to be movable by said ram into and at least substantially through the stock bore for the forcedl passage of the bit through the latter.

4. The combination in apparatus as set forth in claim 3, in which said ram is guided in said nearest guide member and has an axial lost-motion connection therewith.

5. ln apparatus for reforming with a thrust bit a longitudinal bore through elongated stock, the combination with a device for reieasably holding the stock, a push rod for the bit slidably receivable, with its leading end foremost, in the stock bore, and a ram at the trailing end of the push rod and movable axially of the bore in the held stock, of a series of guide members between said device and ram, each guide member having a skirt and aperture means at an end of the skirt for guiding the push rod axially of the stock bore, and said guide members having their skirts telescoped axially of the stock bore and having lost-motion connections with each other and with said device to permit their telescopic extension from the latter over a certain distance and their telescopic contraction in each other and into close proximity to said device with one end of each skirt remaining non-telescoped with the 'next outer skirt, and the guide member nearest said ram` being in the path of forward movement of the latter, and track means supporting the guide member with the outermost skirt and the remaining guide members at said one ends of their skirts for movement axially of the stock bore, the push rod being of sufficient length to be movable by said ram into and at least substantially through the stock bore for the forced passage of the bit through the latter.

6. The combination in apparatus as set forth in claim 5, in which said device has adjacent the end of the stock next to said guide members a guide aperture for the push rod.

7 in apparatus for reforming with a thrust bit a longitudinal bore through elongated stock, the combination with a device for releasably holdingthe stock, a pushrod for. the bit slidably receivable, with its leading end fore# most,l in the. stock bore, and a ram operatively connected with the trailing end of the push rod and movable .axially of the stock bore, and

o 0 of the bore in the heldfstock, of between said device and ram, ing a skirt and aperture means at a series of. guide members an end of the skirt for guiding the push rod axially of the stock bore, and said guide members having their skirts telescoped axially of the stock bore and having lost-motion connections with each other and with said their telescopic device to permit extension from the latter over a certain distance and their telescopic contraction in each non-telescoped with the next outer skirt, and the. guide member nearest said ram with the latter, and track members at said one ends of their skirts for movement axially of the stock length to be movable by said ram into and at least substantially through the stock bore for the forced passage' 9. In apparatus for reforming with a thrust bit a longi the combination tudinal bore through elongated stock,

with a ydevice for axially removably receiving and releasablyholding the stock, and a push rod for the bit slidably receivable, with its leading endv foremost, in the stock bore, of a ram movable axially of the bore in the held stock into and from a certain rear position and axially slidably carrying at its forward end ahead spring-projected toward and operatively connected with adjacent trailing end of the push rod and yieldingly depressible into abutting engagement with the ram, a series of guide members between said device and ram head, each guide'l member having a skirt and aperture means at an end of the skirt for guiding the push rod axially of the stock bore, and said guide members having their skirts telescoped axially of the stock bore and having lost-motion connections with each other and with said device to permit their telescopic extension from the latter over a certain distance and their telescopic contraction in each other and into close proximity to said device with one end of each skirt remaining non-telescoped with. the next outer skirt, and the guide member nearest said ram headl being in the path of forward movement of the latter, and track means supporting the guide member with the outermost skirt and the remaining guide members at said one ends of their skirts for movement axially of the stock bore, the push rod being of sufcient length to bemovable by `said ram into and at least substantially through the stock bore for the forced passage of the bit through the latter, and to depress said head in said rear position of the ram on axial reception of the stock in said device with the bit interposed between the stock and the leadingv for the other stock end and an aperture for the passageA of the bit, said support having a locating seat for said end member for axial alignment by the latter of said other stock end with said bearing aperture and said endmember being movable laterally of the stock betweenv said other stock end and support into seating relation therewith'on axially shifting the stock'and bit against the leading rod end to cause depression of said head in said rear ram position.

ll. ln apparatus for longitudinal tion with a device for releasably holding the stock, a push rod for the bit slidably receivable, with its leading end foremost, inthe stock bore, and a ram at the trailreforming with a thrust bit a each guide member hav-l other and into close prox*l imity to said `device withone end of each skirt remaining:

being operatively connected' means supporting the guide: member with the outermost skirt and the remaining guide i bore, the push rod being of sufcient bore through elongated stock, the combina-- ing end of the push rod and movable axially of the bore in the held stock, of a series of cup-shaped guide members between said device and ram, each guide member having a skirt and a bottom wall with a central aperture for guiding the push rod axially of the stock bore, said guide members having their skirts telescoped axially of the stock bore with their ybottom walls nearest said device, and having lost-motion connections with each other and with said device to permit their telescopic extension from the latter over a certain distance and their telescopic contraction in each other and into close proximity to said device, and said guide members, except the one guide end member next to said device, having outward anges at the top ends of their skirts and the other guide end member ybeing operatively connected with said ram, and a tubular track supporting said one guide end member at its skirt and the remaining guide members at their outward anges lfor sliding movement axially of the stock bore, the push rod being of sucient length to be movable by said ram into and at least substantially through the stock bore for the forced passage of the bit through the latter.

12. The combination in apparatus as set `forth in claim 11, in which said device has adjacent the end of the stock therein next to said guide members a guide aperture `for the push rod.

13. The com-bination in apparatus as set forth in claim 1l, in which said ram is guided in the skirt of said other guide end member and has a lost-motion connection therewith.

No references cited.

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