US2136491A

US2136491A - Metalworking machine

Info

Publication number: US2136491A
Application number: US120124A
Authority: US
Inventors: Elton S Cornell
Original assignee: ABRASIVE MACHINE TOOL CO
Current assignee: ABRASIVE MACHINE TOOL Co
Priority date: 1937-01-11
Filing date: 1937-01-11
Publication date: 1938-11-15
Anticipated expiration: 1955-11-15

Description

Nov.v 15, 1938. E. s. CORNELL METALWOHKING MACHINE Filed dan. 11,

1937 7 Sheets-Sheet l .lllllllll IIII NOV- 15, 1938. E. s. CORNELL,

` METALWORKING MACHINE Filed Jan, ll, 1937 7 Sheets- Sheetl 2 Nov. 15, 1938. E. s. CORNELL METALWORKING MCHINE Filed Jan. 11, 1957 Nov; 15, 1938. E. s. CORNELL 2,136,491

METALWORK I NG MACH INE Filed Jan. 1l, 193'? '7 Sheets-Sheet 4 Nov. 15, 1938.

E. s. 4CORNELL METALWORKING MACHINE Fild Jan. 11, 1937 7 Sheets-Sheet 5 Nov. 15, 1938. E. s. CORNELL METALWORKING MACHINE Filed Jan. ll, 1937 7 Sheets-Sheet 6 NOV. 15, 19,38. El s] CORNELL n 2,136,491

METALWORKING MACHINE Filed Jan. ll, 1937 7 Sheets-Sheet 'T Patented Nov. l5, 1938 UNITED STATES PATENT OFFICE METALWORKING MACHINE Application January 11, 1937, Serial No. 120,124

16 Claims. (Cl. 51-94) This invention relates to metal-working machines and particularly to means for forming and finishing the grooves of so-called twister-guides employed in the manufacture of wire and other attenuated material.

One object of the invention is to provide a de-4 vice for forming and finishing the grooves in twister-guides to produce an extremely smooth surface Without irregularities or flaws liable to scratch or abrade the surface of the wire as itis drawn therethrough during the process of manufacture.

Another object of the inventionis to provide a device of the type indicated which is entirely au-A tomatic in operation and adapted to produce grooves of helical or like conformation.

Another object of the invention is to provide a device of the type indicated which is adjustable to adapt it for finishing grooves of varying twist or lead and which when once adjusted will operate to produce accurate duplication of the work.

Another object of the invention is to provide a device of the type indicated for accurately producing various forms of grooves having continuous straight and helical portions.

Further objects of the invention are set forth in the following specification which describes several forms of construction of the device, by Way of example, as illustrated by the accompanying drawings. In the drawings:

Fig. 1 is a front elevation of a grinding machine incorporating the present inventionl for forming and finishing the grooves of .twisterguides;

Fig. 2 is a plan view of the work-holdingparts of the machine showing their position at the start of the grinding operation;

Fig. 3 is a similar view illustrating the parts at the completion of the grinding operation and the 'manner in which the twister-guide is oscillated with respect to the grinding wheel to cause the groove to be ground in a helical path;

Fig. 4 is an enlarged longitudinal sectional view through the headstock of the machine showing the means for oscillating the work-holder;

Fig. 5 is transverse sectional view through a portion of the machine on line 5 5 of Fig. 2 showing certain elements of the work-holder os- 50 cillating means; v

' Fig. 6 is a front elevational view of a portion of I the machinel showing a modied form of construction of the work-holder oscillating means;

Fig. 'l is a transverse sectional View of the oscil- 55 lating means shown in Fig. 6 illustrating the posigrinding showing a further modified form of construction of the work-holder oscillating means; l

Fig. is an enlarged front elevational view of the work-holder oscillating means shown in Fig. 9 illustrating the parts in the position assumed at the start of the grinding operation;

Fig. 11 is a view similar to Fig. 10 showing the position of the parts at the completion of the grinding operation;

Fig. 12 is a transverse sectional `view of the headstock in this latter modified form of the invention taken on line |2-l2 of Fig. 10;

Fig. 13 is a transverse sectional view on line |3-l3 of Fig. 10 showing the position of the workholder at the start of the grinding operation;

Fig. 14 is a transverse sectional view on line Ill- I4 of Fig. 1l showing the position of the work-holder at the completion of the grinding operation; f Y

' Fig. 15 is aperspective view of one of the complementary sections of a twister-guide showing the twister-groove as finished;

Fig. 16 is an end view yof the two complementary parts of the twister-guide shown in assembled relationship as applied to use; and

,and dimension. After feeding through one set 'of rolls the material is guided to the next set by means of so-called twister-guides. It has been found in practice that in rolling material to produce stock of various shapes in cross-section better results are obtained by presenting the stock to the rolls with its longer transverse axis positioned vertically. The rolls then act to draw out the material, reducing it in size and delivering it with its major axis in horizontal position. Stated briefly, the stock leads to the rolls with its longer axis in vertical position and after being acted upon by the rollsem'erges therefrom with its major axis in horizontal position to be again brought into vertical position before entering the next set of rolls; and so on throughout most of the rolls.

The stock is treated to alter the position of its major axis from horizontal to vertical position between different sets of rolls by means of the twister-guides through which it feeds, see Figs.

- 15, 16 and 17. Grooves of a shape and size corresponding substantially to that of the stock being worked are formed in the guides and arranged helically to provide that during the travel of the stock therethrough it will be twisted and presented to the next set of rolls in the required relationship. The twister-guides are usually constructed in two complementary sections with one-half of the groove formed in each part; the parts being clamped together to form the complete guide as shown in Figs. 16 and 17. It will be readily understood that the grooves of the twister-guides must necessarily be precisely formed, true to shape, accurate as to size and finished with a smooth, polished surface so as to avoid scraping or otherwise marring the surface of the stock drawing therethrough. For many years the grooves in twister-guides have been finished by manually feeding the latter back and forth across a grinding wheel and by scraping, filing and rubbing with abrasive material. None of these methods has proved satisfactory since it is well nigh impossible to produce a groove having its surface free from rough spots, indentations or crevices, the edges of which are liable to abrade the stock being worked. Since the stock passes through the rolling mill in a heated condition and at a rapid rate of feed it is extremely diiiicult to detect imperfections therein. Owing to this fact the amount of scrap or waste occurring during production has been very great, sometimes running as high as eighty percent. of the total output of the mill. To overcome this condition the mill is usually stopped periodically and the twisterguides manually refinished and reassembled in place. This requires considerable time, even though duplicate guides are provided, and thus the productive capacity of the mill is curtailed.

It is the aim of the present invention to provide means for automatically forming and finishing the grooves of twister-guides in a machine capable ofoperating at high speed and accurate in performing the required functions. The machine is preferably provided with a rotating grinding wheel and a table carrying a work-holder for mounting the twister-guide, the wheel or the table being reciprocated, one with respect to the other. The twister-guide is clamped in a holder pivotally mounted on the table and adapted to be rocked about its longitudinal axis during the grinding operation to cause the groove to be ground with a helical pitch. The extent and rate of rocking motion of the holder is adjustable and positively controlled so that the groove may be ground true to form and dimension and with the required degree of twist. In this way the groove may be finished with a mirror-smooth surface, free from imperfections liable to damage the stock to be worked. With the use of twisterguides finished in this manner the quality of the finished stock is greatly improved and the rolling mill may be operated over longer periods of time without stopping to substitute renished guides. The time required to produce deiinite lengths of wire or other stock is thus reduced to a minimum with consequent economies in the cost of manufacture.

Referring first to Figs. 1, 2 and 3 of the present drawings, the base machine as' herein shown is similar in construction to standard surfacegrinding machines now in use but it is to be understood that the present invention may be embodied in machines of other types with either the table or the metal-working tool ,arranged for reciprocatory movement as preferred. The grinding machine comprises a carriage or table 2 mounted for reclprocatory movement in ways at the top of a bed or saddle 3 as shown in Figs. 1, 7 and 8. The saddle 3 may be stationary on the base 5 of the machine or adjustable forwardly and rearwardly thereof.

The grinding wheel 4 may be of usual form carried by a spindle or shaft 6 journaled in suitable bearings in a head or support l which is mounted for vertical sliding movement in guideways formed inthe sides of a stanchion or column 8 rising from the base 5 of the machine, see Fig. 1. The grinding wheel may be driven from any suitable source of power by means of a belt passing around a driving pulley on the shaft 6 and another pulley, not herein shown, which forms one element of the table-reciprocating means. In another form of construction, the table 2 may be stationaryand the head 1 together with the wheel 4 adapted to be reciprocated longitudinally of the table. The periphery of the grinding wheel 4 may be of a contour to grind grooves of any desired cross-sectional shape such as polygonal, being herein Shown as of arcuate shape to adapt it to form semielliptical grooves.

The work g comprising one of the complementary parts of a twister-guide is carried by a rockable work-holder I5 supported between a headstock 25 and a tailstock 26 mounted for adjustment longitudinally of the reciprocating table 2. The work-holder I5 may be in the form of a box, see Figs. 2, 3 and '1, having an open top and provided at its ends with lugs I6 formed with tapered holes for receiving the tapered or pointed ends of the centers or trunnions I1 and I8 of the headstock and

tailstock

25 and 26, respectively, by which the holder is pivotally suspended. Projecting upwardly through bosses on the bottom of the holder I5 are a plurality of screws or bolts I9 for supporting and positioning the work a in the holder; the bolts being locked in adjusted position by means of check-nuts 20 set up against the under side of the holder. The work g is placed in the holder I5 resting on the bolts I 9 with its end engaging a suitable locating pin or bolt 2| projecting inwardly from one end of the holder, after which bolts 22 threaded through tapped holes in the opposite sides of the holder are set up against the sides of the work to secure it flxedly in place.

'I'he tailstock 26 may be of any suitable type and is therefore not herein shown or described in detail. The headstock 25, however, is of novel construction to adapt it for the purpose of both supporting and rocking or oscillating the holder I5. Referring t'o Fig. 4, the tapered center I1 of the headstock 25 is fitted to the bore of a hollow spindle 28 journaled in spaced roller-bearings 29 mounted within the housing or hollow frame 30 of the headstock. The inner race of one roller-bearing 29 is held against a shoulder 3| on the spindle 28 by a nut 32 screwed onto a threaded portion of the spindle; while the inner race of the opposite bearing 29 is held against a similar shoulder 33 on the spindle by a nut 34 screwed onto the threaded end of the spindle. Keyed to the spindle 2l at 35 between the nut 34 and shoulder 33 is a spur-gear 36 which is adapted to be rotated to turn the spindle through a part of a revolution by means of a slidable rack 4l to be later described.

Secured to the reduced end of the center or trunnion I1 by means of a set-screw 4I is a depending clamp or dog 42 having a slot at its lower end for receiving a pin 43 projecting from the end of the holder I5; the pin 43 being held fast. in the dog by a set-screw 44. The headstock may be adjusted longitudinally of the table 2 and secured in place by T-bolts 45 and nuts 46 arranged in the usual manner, after which the set-screws 4I and 44 may be tightened. Rotary motion f the gear 36 is transmitted to the center I1 of the headstock and through means of the dog 42 the workholder I5 together with the work g is oscillated through a part of a revolution for a purpose to be later explained.

Means are providedfor resisting the rotative movement of the work-holder I5 for, a purpose as later explained. This means consists in a friction ring 41 seated in an .annular recess in the side ofthe-gear 36 and normally urged against the face of the gear by means of a piurality of compression springs 46. The-springs 46 are held in pockets 49 in the side of the ring with their ends bearing against adjusting screws 56, see Fig. 4. The screws 56 are threaded into tapped holes in a cover-member 52 fastened to the end of the housing 36 by screws 53.v The friction-ring 41 is held from rotation by projections or splines 54 on its lateral face engaging sockets or keyways 55 on the inner face of the cover-member 52.

The rack-bar 46 is slidably mounted in a guide- Away 56 'formed by transversely-extending vertical and horizontal finished surfaces oil the housing 36 and the inner face of a plate 51 attached to the end of the housing by screws 58.

The forward end of the rack 46, that is, the vend v formed with the rack-teeth, is provided with a central slot 66 which extends the entire length of its toothed portion to receive a bar 6i formed with rack-teeth on its upper surface which substantially aline with the teeth on the main rack 40. As shown in Fig. 5, the inner end of the slot 66 in the rack 46 is provided with a bore 62 for receiving a compression spring 63 which bears against the inner end of the bar 6I to urge it forwardly. Through the last-described form of, construction of the rack 46 any play or backlash between the teeth of the gear 36 and the rack is taken up or compensated for by the reduced end of a stud 66 and surrounding the main shank of the stud is the inner race 61 of a ball-bearing 16. The head 68 of the Vstud 66 abuts the lower end of the race 61 and a nut 69 on the upper threaded end of the stud holds the race firmly against the under side of the rackbar 46. Surrounding the race 61 with balls 12 therebetween is an outer race 1I which serves as a. bowl or roller adapted Kto follow a slot or groove 15 in an inclined track or guide 16 to impart a longitudinal reciprocating movement to the rack-bar 46 during the traverse of the table 2.

As shown most clearly in Figs. 2, 3 and 5, the

bracket 19 fastened to the rearward side of the bed or saddle 3. It has been'explained that oscillatory motion is transmitted to the workholder I5 by'means of the rack 46 and that the longitudinal sliding movement of the rack is effected bythe travel of the roller 1I at its end in the groove 15 of the inclined track 16. The movement of the roller 1I and rack 46 may be controlled to regulate the extent of rocking movement of the work-holder I5 during a predetermined lineal movement of the table 2, this latter movement being usually equal to the length of the work g. As shown in Figs. 2 and 3, theW track 16 has a widened portion at its end opposite from the pivot-stud 11 with a hole therein through which extends the upper threaded end of a T-bolt 82. The T-bolt 62 has its rectangular head slidably engaged in a T-slot 83 formed in the upper surface of an angular bracket 64 bolted to the rearward side of the saddle 3 at 65. The T-slot 83 is formed in an arc concentric with the axis of the stud 11 to provide that the track 16may be swung on its pivot with the T-bolt 82 sliding in the slot. After the track 16 has been adjusted at the desired angle with respect to the direction of movement of the table 2 a 4nut 86 screwed onto the upper threaded end of the T-bolt 82 and set up against the top of the track xedly secures the latter in position. 'I'he opposite end of the track 16 may be held fixed by means of a nut 86 screwed onto the lower threaded end of the pivot-stud 11Aand set up against the under side of the leg 18 of the bracket 19. The upper face of the bracket 64 may be rovided' with an index mark adapted to regisister with graduations 61 scored in the beveled end of the track 16 to indicate the degree of angular adjustment of the track as it is swung on its pivot. As previously explained, the stock passing through the drawing mill must be turned or twisted ninety ,degrees between different sets of drawing rolls and the grooves in the twisterguides form helical guidewaysto impart such turning movement to the stock. The graduations 81 are so calculated and placed as to indicate the required adjustment of the track 16 to eiect proper oscillation of the work during predetermined lengths of traverse thereof in accordance with the desired twist per unit of length. One preferred form of construction of the device having now been described in detail its method of operation will next be explained.

To prepare the machinefor operation a suitable grinding wheel 4 is applied to the spindle 8 and the twister-guide section y placed in the holder I5 and secured in place by the bolts.\22. 'I'he device is herein illustrated, by way of-example, as adjusted to cause the twister-guide section g to be formed with a semielliptical groove which, if continued, would twist with its major axis turning from horizontal to vertical position Within the required distance of say, three feet; this distance being governed by the relation of the guide to the set of the rolls to which it delivers. To effect the required degree of twist the track 16 is swung on its pivot until the graduation marked 3 registers with the index-mark on the bracket 84, after which the nuts 86 and 86 are tightened to nxedly secure the track in place. The machine is then ready for, the operation of forming and finishing the helical groove in the twister-guide section y.

Referring now to Figs. 15, 16 and 17,' the twister-guide G comprises a bottom section g and a topasection g in the form of castings or forgings. The complementary parts d and y' are provided with raised bosses 66 which abut when the parts are placed in juxtaposition in reverse relationship. Substantially midway of their length the members o and g are formed with tapered lugs 80 which are gripped by suitable clamps for holding them in position when applied to use. The two members 9 and y' are formed with concavities at one end to adapt the assembled twister-guide G to be placed in close proximity to the periphery of the rolls from which the material delivers, this end receiving the material with its major axis positioned horizontally. It is a common practice to form the twister-guides with their grooves extending without twist for a short distance from the end and the present drawings illustrate the guidesection y, see Fig. 15, of this form. Since the length of the guide is considerably less than the distance between the pairs of rolls in the drawing mill the groove need twist only a part of the total ninety degree twist to which the material is subjected during its feed between rolls.

Referring now to Fig. 2, at the left-hand end of the track 16 the groove 15 is preferably beveled off at one side as indicated at 90 to provide that the roller 1I may properly enter into and ride out of the groove as the table 2 is reciprocated. The operation of the machine is started in the usual manner by shifting a clutch to connect the grinding wheel 4 and reciprocating means for the table 2 with the drive. As the table travels toward the right. as viewed in Fig. 2, theK-work-holder I5 is traversed therewith and remains nonrotative until the roller 1I enters the groove 15 in the track 16. During the first part of the stroke the abra- Afeeding means for the grinding wheel.

sive wheel 4, indicated by dash lines in Fig. 2, grinds the semielliptical groove in a straight course without twist for a short distance as desired.

Upon entering -t'he groove 15 the roller 1| is caused to move toward the front of the machine simultaneously with its traversing movement toward the right, as viewed in Fig. 3. rI'he roller 1I thus imparts a forward sliding movement to the rack-bar 40 which causes the spur-gear 36 to be rotated to turn thehollow spindle 28 in a clockwise direction as viewed from the right-hand end of the machine. The center' I1 and dog 42 being fast with the spindle 28, the turning movement of the latter rocks the work-holder I5 in the same direction to cause the groove to be ground by the wheel 4 with a helical twist; it being understood that the grinding wheel is fed downwardly in the usual manner during the operation of the machine. Asthe table 2 completes its travel to the right suitable tripping means operate to automatically reverse its direction of traverse while at the same time actuating the During the return 'movement ofthe table 2 the roller 1I travels in the groove 15 to slide the rack-bar 40 rearwardly to rock the work-holder I5 back to initial position to cause the grinding wheel to follow the helical portion of the groove. As the roller 1I runs "out of the groove 15 the abrasive wheel 4 acts to grind the straight portion of the twister-groove while the work-holder I5 remains stable on the centers I1 and I0. The direction of traverse of the table 2 is then reversed again and the wheel 4 fed downwardly to adapt it to continue its grinding action in the groove of the guide-section y in the manner as rst explained.

After the groove in the guide-section g has been ground to the correct dimensions, shape and twist, the machine is stopped and the work removed therefrom. The complementary part U may then be placed in the holder I5 and the groove ground therein in the same manner. When the two guide-sections g and a' are properly iinished by the grinding operation they may be clamped in position as illustrated in Figs. 16 and 17 to form the groove elliptical throughout its full length with its major axis twisting from a horizontal piane to a plane at the required inclination to the horizontal as required by the arrangement of the drawing rolls in the mill.

As previously explained, the machine may be adjusted tocause it to grind the twister-grooves with part of their length straight and part twistmg. It will be understood, however, that the machine may be adjusted so that the roller 1I will remain in the groove 15 to grind the groove with a continuous helical twist. By limiting the length of .the track 16 and providing a bellmouth entrance at either end of its groove 15 the roller 1I may be caused to leave the groove at both ends thereof to grind the grooves with straight portions at both ends.

By loosening the set-screw 4| and turning the dog 42 to different positions of adjustment the work-holder I5 may be turned on the pivots I1 and I8 until the upper surface of the twisterguide g or g is inclined at different angles to the wheel 4 so that grooves having the major axis initially inclined at any desired angle to the horizontal may be produced in the machine. In grinding the straight lengths of the groove while the roller 1I is beyond the end of the track'16 the tendency of the work-holder I5 is to remain level under the action of gravity due to its pendulus mounting. When the work-holder I5 is set at an angle to the wheel 4, however, its tendency to swing back to horizontal position is resisted by the friction-ring 41 which acts in the manner of a brake-shoe to prevent rotation of the gear 36 when the roller 1| is beyond the end of the groove 15.

Figs. 6, '7 and 8 illustrate a modied form of construction of the device in which the workholder I5 is suspended between pointed trunnions 94 carried by opposite tailstocks 95 adjustably mounted on the reciprocating table 2. Bolted to the side of the work-holder I5 is an arcuatelyshaped bracket 91 formed with a helical groove 08 having straight portions $9 at its ends extending in parallel relation to the axis on which the track swings. Engaged in the groove 98 is a roller |00 carried by a stud 0| fast in the upper end of an arm |02 rising from the saddle 3 of the machine. Y

The method of operation of the last-described device is substantially the same as that of the first-described form o! construction. As the table 2 is reciprocated the xed roller |00 rides in the groove 98 of the bracket 91 to swing the work-holder I5 on its pivots 94. In this manner the work-holder is rocked from the horizontal position shown in Fig. 'Ito the inclined position illustrated in Fig. 8 to cause the groove in the twister-guide section g to be ground with a straight portion which changes to a helical path as the roller first rides in the straight end 90 and then in the helical portion 90r of the groove in the bracket 91. It will be understood that different brackets 01 having various forms of grooves may be substituted for the one herein shown whereby to adapt the machine for grinding twister-grooves of varying twist or lead.

Figs. 9 to 14, inclusive, illustrate a still further modied form of construction of the means for rocking the work during its travel with respect to the grinding wheel. In this latter form the work-holder I5 is pivotally'supported at its ends on the pointed trunnions |06 and |01 of the tailstock |09 and headstock IIO, respectively. 'Ihe tailstock may be of any suitable type while the headstock I0 is of novel construction as next described. A spindle rotatably mounted in the headstock H0 carries the trunnion |01 at one end and a worm-wheel 2 at its opposite end. On the projecting end of the trunnion |01 is adjustably mounted a clamp `or dog 3 having its lower end slotted to receive the spherical end of a stud Ill projecting from the end of the workholder l5. Referring now to Fig. 12, the headstock housing is bored to receive a transverselyextending shaft H formed at its inner end with a worm IIS which meshes with the worm-wheel |I2. On the opposite end of the shaft H5 is ilxed a spur-gear |20, this end oi the shaft being journaled in a bearing block ||1 fastened to the side of the headstock housing. Mounted to slide in the bearing block |'|1v above the gear |20 is one end of a relatively long bar I2| having rackteeth on its under side which mesh with the teeth of the gear. As shown in Fig. 9 the opposite end of the rack-bar |2| is flxedly secured to the end of an angular arm |22 fastened to the side of the saddle 3 of the machine.

Asthe table 2 is reciprocated with respect to the grinding Wheel`4 the shift.||5 is rotated by the gear |20 as the latter travels along the rackbar |2| in mesh with the teeth thereof. Rotary motion is transmitted from the shaft |I5 to the spindle and trunnion |01 of the head-stock ||0 through the worm ||6 and Wheel |I2. As the trunnion |01 is turned it acts through the dog H3 and stud H4 to oscillate the work-holder I5 and the work g carried thereby. In this mannerthe work is swung iirst in one direction and then in the opposite direction duringthe traversing motion of the table 2 to cause the groove to be ground in with ahelical-twist. To provide for grinding the twister-groove with a straight portion the inner end of the bar |2| is formed with-l out rack-teeth as -indicated at |23 so that during the initial part of the traversing stroke of the table 2 the gearing remains inoperative.

It `will be observed from the foregoing that the present invention provides a machine for forming and finishing twister-guide grooves with varying lengths of straight and helical portions as required. The machine is automatic in operation and adjustable to adapt it for grinding twistergrooves of various forms; when once adjusted being capable of duplicating the work to produce` I twister-guides of accurate form and dimensions.

. With the -use of the present improvedmachine the guides may be ground very rapidly with their grooves finished without aws so that they maybe employed -continuously for longer periods oi time without reinishing Due to the fact that the twister-grooves are formed automatically and mechanically without requiring subsequent handflnishing operations, the guidesl may be constructed `from relatively hard metal of dense and flawless structure, capable of withstanding high temperatures and durable over long periods of use.

While the machine is herein shown and described as embodied in several preferred forms of construction, it is to be understood that various other modications may be made in the structure and arrangement of the parts thereof without: departing from `the spirit or scope of the invention. Therefore, without Hunting myself in this respect, I claim: l

1. In a machine of the type indicated, a rotating tool, a table reciprocable with respect to the tool, a work-holder rockably 'mounted on the table, a gear operatively connected to the workholder, a slidable rack having teeth meshing with the' gear, a relativelyflxed inclined track, a follower on the rack slidable on the track during the movement of the table, and means for preventing back-lash between the rack and gear comprising a toothed bar `slidable longitudinally of the rack with its teeth meshing with the gear, and resilient means acting between the rack and toothed bar to normally urge ,the latter longitudinally of the rack to compensate for play between the rack and gear.

2. In a metal-working machine, a tool, a table, means for relatively reciprocating said tool and table, a. work-holder, means for -grockably mounting the work-holder for pendulous oscillation on the table, and automatically-operated means for rocking said work-holder duringi the relative reciprocation of the tool and table to oscillate the surface of the Work about an laxis located above the workingrface of the tool, said last-named means being operative in timedl relation to the relative reciprocation of the tool and tablelto rock the work-holder in one direction as the tool traverses the work during, one stroke Tand to rock the Work-holder in the opposite direction as the tool traverses the work during a reverse stroke.

.l In a machine for forming helical grooves in twister-guides, a rotating too1,a table, means for relatively traversing the tool and table, a Workholder, means for mounting the work-holder on the table to adapt it to oscillate the work about an axis at right-angles to the axis of the rotating tool and to contact the tool with the Work at a greater distance from the axis of rotation of the tool than from the axis of oscillation of the workholder, and automatically-operated means for oscillating the work-holder during the relative traverse of the tool and work. A

4; In a machine for forming helical grooves in twister-guides, a rotating tool, a table .'means for relatively traversing the tool and table, a work-holder beneath the tool, means for pendulously mounting the work-holder on the table to adapt it to oscillate .the work about an s at right-angles to the axis of the rotating t`ofol and to contact the tool with the Work below the axis of oscillation of the work-holder, and means automatically operative in timed relation to the relative traverse of the tool and table to rock the work-holder in one direction as the tool traverses the Work during one stroke and to rock the workholder in the opposite direction as the tool traverses the work during a reverse stroke.

5. In a machine for forming helical grooves in twister-guides, a grooving tool, a table, means for holder beneath the tool, means for `pendulously mounting the work-holder on the table toadapt it to oscillate the/work to contact the tool therewith below the axis\cf oscillation of the workholder, and means operative in timed relation to the relative traverse of tool and table to rock the work-holder in one direction as the tool traverses the work during one stroke and to rock the work-holder in the opposite direction as the tool traverses-the work during a, reverslis'trplfge comprising a gear, a rack for rotatingithgi'gear, and means for reciprocating the rack the rela- `tive traverse of the tool and work. I

6. In agmachine for forming helical grooves in twister-guides, a grooving tool, a table reciprocable with respect to the tool, a work-holder beneath the tool, means for pendulously mountingA the work-holder ori the table to adapt it to oscillate the work to contact the tool therewith below the axis of oscillation of the work-holder, and means 'operative in timed relation to the reciprocation of the table to rock the work-holder in one direction as the tool traverses'the work during one stroke and to rock the work-holder in the opposite direction as the tool traverses the work during a reverse stroke comprising a track inclined to the direction of traverseof the table, a rack carried by and slidable laterally of the table, a follower on the rack slidable on the track, and a gear rotated by the rack and connected to rock the work-holder.

7. In a machine for forming helical grooves in twister-guides, a grooving tool, a table reciprocable with respect to the tool, a work-holder, means for pendulously mounting the work-holder on the table to adapt it to oscillate the work to contact the tool therewith below the `axis of oscillation of the work-holder, and means for oscillating the work-holder during the reciprocating movement of the table comprising a gear connected to the Work-holder, a rack for rotating the gear, a track inclined to the direction of traverse of the tabel for actuating the rack, and means for adjusting the inclination of the track to regulate the degree of oscillation of the holder.

B. Ina machine for forming grooves in twisterguides, a grooving tool, a table, means forrelatively traversing the tool and table, a kworkholder, means for pendulously mounting the work-holder on the table to adapt it to oscillate the work to contact the tool therewith below the axis of oscillation of the work-holder, and means for oscillating the work-holder during the traverse of the tool on the work comprising a gear con- `nected to the work-holder, a rack slidable transversely of the table for rotating the gear, a follower or'i the rack, and a relatively xed guideway having straight and inclined portions, said follower being slidable in the guideway t actuate the rack and rock the work-holder to cause the work to be grooved in both straight and helical paths.

9. In a machine of the type indicated, a rotating groove-forming tool, a table reciprocable with respect to the tool, a work-holder. means for pendulously mounting the Work--holderl on the table to adapt it to oscillate the work to contact the tool therewith below the axis 'of oscillation of the work-holder, a gear connected to oscillate the work-holder, a rack having its teeth in mesh with the gear, a follower on the rack, a track on which the follower travels during the reciprocatory movement of the table to cause it to oscillate the work-holder, and friction means for resisting turning movement of the'holder during a portion of the movement of the table.

10. In a machine for forming helical grooves in twister-guides, a grooving tool, a table, means for traversing the table with respect to the tool, a work-holder, means for pendulously mounting the work-holder on the table to adapt it to oscillate the work to contact the tool* therewith below the axis of oscillation of the work-holder, automatically-operated means for oscillating the work-holder during the relative traverse of the work and tool comprising an inclined guideway on the holder, and stationary means engageable with the guideway to cause it to oscillate the work-holder, during the reciprocation of the table.

11. In a machine for forming grooves in twisterguides, a grooving tool, a table, means for reciprocating the table with respect to the tool, a workholder, means for pendulously mounting the workholder on the table to adapt it to oscillate the work to contact the tool therewith below the axis of oscillation of the work-holder, a guideway on the work-holder having inclined and straight portions, and a relatively stationary follower engaging the guideway to oscillate the wolk-holder during portions of the reciprocating stroke of the table without oscillation thereof during other portions of the stroke.

l2. In a machine for forming helical grooves in twister-guides, a grooving tool, a table reciprocable with respect to the tool, a headstock and tailstock on the table., a Work-holder pendulously mounted between the centers of the headstock and tailstock to adapt it to oscillate the work to contact the tool therewith below the axis of oscillation of the work-holder, means to rotatively connect the headstock center and work-holder, a gear on said center, and a xed rack extending longitudinally of the table and connected to rotate the gear in timed relation to the relative reciprocation' of the tool and table to rock the work-holder in one direction as the tool traverses the work during one stroke and to rock the work-holder in the opposite direction as the tool traverses the work during a reverse stroke.

13. In a machine for forming helical grooves in twister-guides, a grooving tool, a table, means for relatively traversing the tool and table, a work-holder beneath the tool, means for pendulously mounting the work-holder on the table to adapt it to oscillate the work to Contact the tool therewith below the axis of oscillation of the work-holder, and means operative in timed relation to the relative traverse of the tool and table to rock the Work-holder in one direction as the tool traverses the work during one stroke and to rock the work-holder in the opposite direction as the tool traverses the work during a reverse stroke comprising a worm-wheel operatively connected to the work-holder, a worm meshing with the wheel and carrying a gear, and a fixed rack engaging the gear to rotate the latter first in one direction and then in the opposite direction during the reciprocation of the table.

14. In a machine for forming helical grooves in twister-guides, a grooving tool, a work-holder beneath the tool, means for relatively traversing the tool and work-holder, means for pendulously mounting the work-holder to adapt it to oscillate the work about a xed axis extending in the direction of said traverse, said axis of oscillation for the work-holder being coincident with the axis of the. groove to be formed in the work, and means automatically operative in timed relation to the relative traverse of the tool and workholder to rock the work-holder in one direction as the tool traverses the work during one stroke and to rock the work-holder in the opposite direction as the tool traverses the work during a reverse stroke.

,15. In a machine of the typel indicated, a rotating groove-forming tool, a table reciprocable with respect to the tool, a headstock and tailstock on the table, a work-holder pendulously mounted between the centers of the headstock and tailstock to adaptit to oscillate the work to contact thetool therewith below the axis of oscillation of thework-holderx means to rotatively connect the headstock center and work-holder, a gear on said center, a rack slidable transversely of the table with its teeth in mesh with the gear, means for sliding the rack during a portion of the stroke of the table, and means operative to hold the gear against rotation during other portions of the stroke whereby the work will be grooved both straight and helically.v

16. In a machine for forming helical grooves in twister guides, a grooving tool, a work-holder beneath the tool, means for relatively traversing the tool and work-holder, means for pendulously mounting the work-holder to adapt it to oscillate the work about a xed axis extending in the direction of said traverse, said axis of oscillation for the .work-holder being coincident with the axis of the groove to be formed in the Work, means automatically-operative in timed relation to the relative traverse of the tool and Workholder to rock the work-holder in one direction as the tool traverses the Work during a portion of one stroke and to rock the Work-holder in the opposite direction as the tool traverses the Work during the same portion of a reverse stroke, and means operative to hold the Work-ho1der-from oscillation during other portions of said strokes whereby the work will be grooved both straight and helically.

ELTON S. CORNELL.