US3037409A

US3037409A - Center adjusting device

Info

Publication number: US3037409A
Application number: US861640A
Authority: US
Inventors: Milton D Hare; Hector A Meneses
Original assignee: Research Corp
Current assignee: Research Corp
Priority date: 1959-12-23
Filing date: 1959-12-23
Publication date: 1962-06-05
Anticipated expiration: 1979-06-05

Description

June 5, 1962 M. D. HARE ET AL 3,037,409

CENTER ADJUSTING DEVICE Filed Dec. 23, 1959 6 Sheets-Sheet 1 INVENTORS MILTON D. HARE HECTOR A. MENESES ATTORNEYS June 5, 1962 M. D. HARE ET AL 3,037,409

CENTER ADJUSTING DEVICE Filed Dec. 23, 1959 6 SheetsSheet 2 INVENTOR5 MILTON D. HARE HECTOR AMENESES BY //4A04/f5 ATTORNEYJ June 5, 1962' M. D. HARE ET AL 3,037,409

CENTER ADJUSTING DEVICE Filed Dec. 2:5, 1959' 6 Sheets-Sheet s T' I 749 i 8 q 8% H 2 .J g /g q- 0) 8 I: @835 g f" 1 H I g! O L8 9 8 m 3/ o g L; m 802 383 i 1a a E 5| w/ 8 8 a" 7 3 Y 3 3 i 3 I s 8 2 IE] 8 g I *2 3 INVENTORS MILTON D. HARE HECTOR A. MENESES ATTORNEYS M. D. HARE ET AL CENTER ADJUSTING DEVICE June 5,' 1962 6 SheetsSheet 4 Filed Dec. 23, 1959 5 5 \9m m s m 9m m x m m w ma 3m mE A 3 om DM m i 0mm N 9m 09 I mo mm. mm a Q. 4 4 2% MH 8 3 0S v wq 3 mm v .Y B w 7 v: on K m mm mp 0F mm om mm Q ow @m www June 5, 1962 M. D. HARE ET AL 3,037,409

CENTER ADJUSTING DEVICE Filed Dec. 23, 1959 6 Sheets-Sheet 5 llO INVENTORS MILTON D. HARE HECTOR A. MENESES BY jaw/"5M 92 94 84 ATTORNEY;

June 5, 1962 M. D. HARE ET AL 3,

CENTER ADJUSTING DEVICE Filed Dec. 25, 1959 6 heets-Sheet 6 IN VE N TORS MILTON D. HARE HECTOR A. MENESES ATTORNEYS United States Patent 3,037,409 CENTER ADJUSTING DEVICE Milton D. Hare, Los Altos, and Hector A. Meneses,

Mountain View, Calif., assignors to Research Corporation, New York, N.Y., a corporation of New York Filed Dec. 23, 1959, Ser. No. 861,640 9 Claims. (CI. 82-45) This invention relates to center adjusting devices having particular utility on machines including a spindle adapted to rotate work holding means.

There is a particular need in the industry to provide means for lathes, and boring, reaming, and honing machines and the like, whereby structures held in work or tool holding devices may be accurately centered for rotation with the rotatable spindle or offset therefrom a predetermined amount. The need is particularly great where the work holding structure comprises independently movable, plural jawed chucks and Where the work piece is unsymmetrical.

It is a principal object of the present invention to provide in a rotating spindle machine having a work holding member means for mounting the work holding member for selective radial movement relative to the axis of rotation of the spindle whereby the work may be accurately centered or offset a predetermined amount.

A further object is to provide such a device wherein the work holding means may be rapidly and accurately adjusted relative to the axis of rotation of the spindle of the machine.

A further object is to provide such a device that is relatively simple as to its parts, easy to operate and which materially reduces the time required to center or oifset a work holding member relative to the axis of rotation of the drive spindle.

These and other objects and advantages are provided by a center adjusting means for a machine having a rotatable spindle and a work holding member comprising means mounting the work holding member in driven relation to the spindle, said mounting means including a plurality of means having cam surfaces mounted for rotation with the spindle and selectively displaceable radially of the axis of rotation of the spindle, means securing the work holding member to the means having cam surfaces, cam followers for selectively moving the means having cam surfaces radially of the axis of rotation of the spindle, and locking means securing the means having cam surfaces against radial displacement relative to the axis of rotation of the spindle.

These and other objects and advantages will be more apparent to those skilled in the art from the following detailed description of the invention when considered with reference to the accompanying drawings wherein:

FIG. 1 is an elevational view of the live center or headstock end of a hollow spindle type lathe incorporating the improvements of the present invention;

FIG. 2 is a front elevational view of the headstock of the lathe illustrated in FIG. 1 with the chuck removed to show the improvements of the present invention;

FIG. 3 is a vertical sectional view of the headstock of the lathe shown in FIGS. 1 and 2 substantially on line 33 of FIG. 2;

FIG. 4 is a transverse section through the headstock of the lathe illustrated in FIG. 2 substantially on line 44 thereof;

FIG. 5 is an exploded view of the mounting means for the work holding chuck of the lathe illustrated in FIGS. 1 through 4;

FIG. 6 is an enlarged fragmentary view of the mounting means permitting radial movement of the work holding chuck relative to the axis of rotation of the spindle of the lathe;

FIG. 7 is an enlarged view of the cam surface elements embodied in the improved adjustable mounting means of the present invention;

FIG. 8 is a diagrammatic view showing the development of the front pair of cam surfaces; and

FIG. 9 is a similar diagrammatic View showing the development of the rear pair of cam surfaces.

Referring to the drawings, 10 generally designates a lathe incorporating the improvements of the present invention and comprises a bed portion 12 and a headstock 14 slidably mounted on the bed 12. The headstock 14 includes a housing which rotatably mounts a spindle 16 in conventional bearing means 18 and 20. The spindle 16 has teeth 22 cut in a portion thereof which teeth are engaged by a timing chain which is driven by the lathe motor through suitable change speed and reverse gear means not shown in the drawings or forming part of the present invention.

A draw bar 26 is received within the 'bore 28 in the spindle of the lathe. The forward end of the draw bar 26 is provided with external threads 30 which threads project forwardly of the most forward edge 32 of the hollow spindle 16 of the lathe. The rearward end of the draw bar 26 receives an annular knob or handle 34 which knob is secured to rotate with the draw bar. Concentrically spaced about the inner face of the annular handle 34 are a plurality of large bores 36 and a plurality of small bores 38. The small bores receive threaded pins 40 with the head ends of the pins passing through bores in a locking ring element 42 whereby the pins 40 mount the locking ring member 42 to the annular handle member 34 but permit relative axial movement therebetween.

Within each of the large bores 36 is a helical compression spring 44. Each of the helical draw bar compression springs 44 receives at the forward end a pin generally designated 48. Each pin has a reduced diameter shank portion 50 and a head portion 52. The shank portion 50 of each pin is adapted to be slidably received in its respective helical spring while the head portion 52 of each pin is snugly slidable in its large bore 36. The head portions of the pins engage face 54 of the locking ring 42 and a ball race 56 is formed in the opposite face which race receives a plurality of ball bearing means 58. As clearly illustrated in FIGS. 3 and 4 of the drawings, the ball race 56 is so positioned that the balls 58 thereof engages end 60 of the hollow spindle 16 of the lathe.

The forward end of the spindle 16 is received in a large bore 6 2 in the lathe face plate 64. A plurality of set screws 66 threadedly received in radial bores in the face plate 64 secure the face plate to the spindle with the base of the set screws engaging a set screw slot 70 V formed in the forward end of the spindle 16 as more clearly shown in FIG. 4 of the drawings whereby as the timing chain 24 rotates the spindle 16, the face plate 64 is also rotated.

A conventional work holding chuck generally designated 76 is rotated by the face plate 64 and the work holding chuck 76 is laterally movable relative to the face plate 64 through the cooperative connection between the following elements interposed between the face plate 64 and the chuck 76: anti-twist plate 78, cam plate member 80, draw bar nut 82 and cam plate member 84. These elements are shown in assembled relationship in FIGS. 3, 4 and 6 and in an exploded form in FIG. 5. The chuck 76 which is illustrated as a conventional four-jawed type is secured to the front cam plate 84 by set screw means 86 which are threadably received in the chuck and engage a set screw groove 88 at the forward end of the cam plate 84. The cam plate 84 is provided with a cam groove generally designated 90 which cam groove defines an inner cam surface 92 and an outer cam surface 94.

Cam surfaces

92 and 94, as will be more fully described with reference to FIG. 8 are generally non-circular and eccentric to the center bore in the cam plate 34 and to each other and the peaks thereof are radially opposed.

Cam plate 80 is also provided with a cam groove generally designated 96 which cam groove defines an inner cam surface 98 and an outer cam surface 180.

Cam surfaces

98 and 100 are generally non-circular and eccentric to the center bore in the cam plate and to each other and the surfaces are closest together adjacent zone Y. The development of

cam surfaces

98 and 100 will be described hereinafter with reference to FIG. 9.

Cam plate 84 is rigidly secured to cam plate 80 by a plurality of bolts 102 which pass through bores 194 in cam plate 84 and engage tapped bores 106 in the cam plate 80. In securing cam plate 84 to cam plate 80, the peaks of

cam surfaces

92 and 94 of

plate

84 and 98 and 100 of plate 80 are displaced 90 from one another.

The back face of cam plate 84 and the front face of cam plate 80 are recessed as at 108 and 110, respectively, to receive therebetween the draw bar nut 82. As more clearly shown in FIG. 6, the diameter of the draw bar nut 82 is less than the diameter of

openings

108 and 110 in the respective cam plates and the thickness of the draw bar nut 82 is less than the total depth of the

openings

108 and 110 in said cam plates whereby the

cam plates

80 and 84 are selectively movable with respect to the draw bar nut as to be more fully described hereinafter.

The draw bar nut 82 is provided with internal threads 112 which mate with threads 30 on the draw bar 26. In assembled form, the nut 82 is screwed onto the cooperating threads 30 at the forward end of the draw bar and the draw bar nut 82 is also secured to the face portion 72 of the face plate 64 by three screws 114 which are threadably received in three tapped bores 116 in the face porden 72 of the face plate 64. Referring particularly to FIG. 6, it will be noted that the bores 118 in the draw bar nut 82 for the screws 114 are larger than the screw shanks and the bores 118 each receive a bushing 120 having an axial length greater than the lip 122 formed about the bore 120 by counterbore 124 whereby when the screws 114 are cinched, the draw =bar nut 82 rotates with the face plate 64 which, in turn, brings about the rotation of the draw bar 26 and its annular handle member 34 at the rearward end of the draw bar. The bores in the draw bar nut 82 are at least %2-IflCh larger than the outside diameter of the bushings 128. This provides limited radial movement therebetween to permit ease of engagement between the nut 82 and the threads on the draw bar. Through the use of the spacer bushings 120, the draw bar nut 82 also has limited axial movement relative to the spindle 16 and the face plate 64 which movement is controlled through the draw bar handle 34 as to be more fully described hereinafter.

The anti-twist plate 78 couples the rear cam plate 80 and, therefore, the front cam plate 84 and the chuck 76 to the face plate 64. As more clearly shown in FIG. 5, the anti-twist plate 78 is provided with four

slots

121, 123, 124, and 125 which extend from the inner peripheral edge 126 radially outward toward the outer peripheral surface 128 thereof. The depth of the

slots

121, 123, 124, and 125 determine the amount of lateral displacement of the chuck 76 relative to the axis of rotation of the spindle 16, and the

slots

121, 123, 124 and 125 are circumferentially spaced 90 from each other.

The face plate 64 is provided with a pair of

slots

128 and 130 displaced 180 from one another and each of these slots has secured thereto, by screws 132, slide block elements 134 and 136, respectively, as more clearly shown in FIG. 3 of the drawings. The thickness of the slide blocks 134 and 136 is greater than the depth of the

slots

128 and 130 in the face plate 64 by an amount sub- 4. stantially equal to the thickness of the anti-twist plate 78. These slide blocks 134 and 136 are received in slots 121 and 123 of the anti-twist plate and prevent relative rotative motion between the anti-twist plate 78 and the face plate 64. The back face of cam plate is similarly provided with a pair of slots 138 and 140, FIGS. 4 and 5, which slots receive similar slide blocks 142, one of which is illustrated in FIG. 4. The slide blocks 142 are received in slots 124 and of the anti-twist plate 78 and prevent relative rotative movement between the cam plate and the face plate 64.

From the foregoing description, it will be seen that as the spindle 16 rotates, the chuck 76 is also rotated due to the interconnection of the

cam plates

80 and 84 to the face plate 64 through the slide blocks carried by the face plate 64 and the rear cam plate 80 which cooperate with the spaced radial slots in the anti-twist plate 78. It will also be seen that the chuck 76, the two

cam plates

80 and 84 and the anti-twist plate 78 are free to slide within limits with respect to the face plate 64.

Thus it will be seen that the transmission of torque or rotational drive to the chuck is through the anti-twist plate 78 and any frictional effects between the plate 78 and the cam plate 80 and the face plate 64 are incidental as far as rotational drive for the chuck is concerned.

The headstock 14 supports a pair of plate members and 152 disposed at right angles to each other. The top plate member 150 is secured to the headstock 14 by screw means 154 and adjacent the rearward end of the plate 150 is secured a boss 156 by screw means 158. The boss 156 pivotally mounts a lever plate 160 on pivot pin 162. Adjacent the forward end of lever plate 160 is a cam follower block 164 which carries at its lower edge a cam follower 170. The cam follower is circular in plan and rotatably mounted on the extended end of the bolt 172, secured to the block 164.

The diameter of the cam follower 170 is such that it is substantially in engagement with the inner and outer cam surfaces 98 and 100 of cam plate 80 at point Y, FIG. 7, adjacent the cam peaks where the two cam surfaces are closest together. The cam lever 160 is pivoted about the pin 1.62 to move the cam follower 170 and thus shift the relative position between cam plate 80 and face plate 64 by rotation of the cam runout knob assembly generally designated 174.

The cam runout knob assembly 174 includes a hand knob 17 6 keyed to a shaft 178 which shaft is threadably received in a bushing 180. The bushing 180 is received in a sleeve 182 secured in the front cam block 164 and as more clearly shown in FIG. 3 of the drawings, the bushing 180 is provided with a flange 184 which cooperates with a flange on the sleeve 1S2. Seated between the upper surface of the bushing 180 and an annular nut 186 threaded into the upper end of the sleeve 182 is a helical compression spring 188. The lower end of the shaft 178, secured to the hand knob 176, abuts a hearing plate 190 inset in the upper angle plate 150. By rotating the handle 176 in one direction, the shaft 78 is screwed toward the bearing plate 190 by cooperative engagement with the internal threads on the bushing 180 causing the plate 160 to move upwardly which, in turn, urges the cam follower 170 in an upward direction. If the hand knob 176 is rotated beyond the limits of movement of the cam plate 80 relative to the face plate 64, continued rotation of the knob 176 causes the bushing 188 to move the shaft 178 and its handle portion 176 upwardly against the tension in spring 188 preventing damage to the assembly.

By rotating the hand knob 176 in the opposite direction the cam lever plate 160 is moved downwardly by helical compression spring 192. Helical compression spring 192 is received about a post 194 threadedly mounted in a bore in angle plate 150 and in the upper surface of the headstock 14. The post 194 passes through a large opening 196 in the cam lever plate 160 and the upper end of the post 194 is center bored and tapped as at 198 to receive a screw 200. The screw 200 mounts a cap piece 202 to the post 194 whereby the helical spring 192 acts between the lower surface of the cap 202 and the upper surface of the lever plate 160. The compressive force of the spring 192 may be adjusted by means of the cap attaching screw 200.

The force applied to cam lever plate 160 by spring 192 is sufiicient to move the chuck 76 and the

cam plate

80 and 84 downwardly across the face plate 64 during normal adjustment but is not suflicient to move these elements when the mechanism is in the locked position. During normal operation the force due to helical spring 188 is suflicient to balance the force of spring 192 and also to move the chuck and the cam plates upward across the face of the face plate 64, as hereinbefore described. Thus, springs 188 and 192 protect the mechanism from damage which might result from attempts to force the mechanism beyond, for example, the A; lateral displacement for which the cam surface means of the illustrated form of invention are designed.

Referring to FIGS. 1, 2 and 4, angle plate 152 pivotally mounts on block 206 a second cam lever plate 208 which is displaced 90 from cam lever plate 160. Cam lever plate 208, like cam lever plate 160, includes a hand operated cam lever plate adjusting handle 210 including an overload spring assembly 212 which functions in the manner described with reference to the hand knob control assembly 174 described with reference to FIG. 3 of the drawings. The reverse direction of movement of the cam lever plate 208 is brought about by the return spring assembly generally designated 214 which is structurally and functionally the same as the return spring assembly described With reference to FIG. 3 and will not therefore be described in detail.

The forward end of the cam lever plate 208 carries a generally U-shaped bracket member 216 which supports on one leg thereof a cam follower assembly generally designated 218. The cam follower assembly 218 includes a cam roll 220 which is received in groove 90 between cam surfaces 92 and 94 and has a diameter substantially equal to the closest spacing B between the peaks of cam surfaces 92 and 94 as illustrated in FIG. 7 of the drawings.

By manual adjustment of the cam lever plate 208 adjusting knob 210, the chuck 76 and the attached

0am plates

80 and 84 are moved inward and outwardly in a direction 90 displaced from the movement of said cam plates and chuck brought about by movement of the hand control knob assembly 174.

As hereinbefore set forth, the cam surfaces, employed in laterally shifting the chuck reltaive to the axis of the spindle, are four in number, non-circular, and are eccentric to the bore in their respective cam plate.

Referring to FIGS. 8 and 9, the development of cam surfaces 92 and 94 and 98 and 100 are illustrated. In the illustrated form of the invention, each

cam surface

92, 94, 98 and 100 comprises three arcs. For example, cam surface 94 comprises arcs A C and D having centers A, C, and D respectively as ilustrated in FIG. 8. It will be noted that arcs forming the cam surfaces may be blended as at B and D where the arcs intersect to provide a smoothly curved cam.

While specific forms of cam surfaces have been illustrated, it will be apparent to those skilled in the art that substantially any form of eccentric cam surfaces could be employed in the device. Further, it will be apparent to those skilled in the art that each of the four cam surfaces may be provided on a separate cam plate instead of combining two cam surfaces, one internal and one external, on each cam plate whereby a single cam follower may be employed for a pair of cam surfaces as in illustrated form of the invention.

Operation In operation of the improved centering mechanism of the present invention, the material to be worked is mounted in the jaws of the chuck 76. The handle 34 is rotated in a direction to back the draw bar 2'6 from the draw bar nut 82 which, in turn, relieves the force applied, by the plural helical springs 44, to the draw bar nut 82 which, in turn, relieves the force applied by the nut against the face of the groove 110 cut in the forward face of the cam plate 80. This, in turn, reduces the friction between the cam plate 80, the anti-twist ring 78 and the forward face of the face plate 64 permitting limited lateral motion between cam plate 80 and the laterally fixed chuck plate 64. It will be particularly noted that reducing the friction between the cam plate 80, the anti-twist ring '78 and the front face of the face plate 64 does not effect the drive from the spindle 16 to the chuck 76 as this drive is through the cooperation between the four

slots

121, 123, 124, and 125 in the antitwist ring 78 and the two slide blocks 134, 136, secured to the face plate 64 and the two slide blocks 142 secured to the back face of cam plate 80. The spindle is then rotated and the operator applies, for example, a dial indicator or shadowgraph to the work and either hand knob 176 at the top of the headstock or the knob assembly 210 on the side of the headstock 14 is adjusted to bring the runout of the work to a minimum. Ideally, the remaining runout can be removed by rotation of the other of the hand knob; however, in actual practice it has been found that several successive adjustments of both of the

knobs

176 and 210 are usually required as it is difficult to make a fine adjustment for one component of motion when the runout due to the other component is large. It has been found, however, that an experienced operator can reduce the runout to less than $0001 inch in less than a minute and to less than 10.0002 inch in about three minutes. After the adjustment of the

knobs

176 and 210 is complete and the runout of the work is at a minimum, with or without stopping the machine, the operator tightens the draw bar by means of the handle 34 to lock the mechanism in its centered position. The locking takes place by causing the draw bar 26 to be screwed further into the draw bar nut 82, increasing the force on the springs 44 and drawing the draw bar and its handle assembly 34 inwardly which, in turn, increases the force applied by the draw bar nut 82 against the face of the groove in the cam plate 80. This increases the frictional engagement between the rearward face of the cam plate 80 and the face plate 64 through the anti-twist ring 78. In general, the draw bar is never completely slackened off since the spring pressure is used to provide some radial friction while making radial adjustments so that the chuck assembly remains in the position it was placed by the last adjustment of the cam adjusting control member.

If the operator wishes to displace the work laterally by a known amount, the operator chucks the Work so that the desired displacement will be towards the peaks of the cam surfaces 92 and 94. The Work is then centered as previously described and the lathe is stopped with the peaks, point B, of the cam surfaces 92 and 94 in contact with their cam roller 220. The dial indicator or shadowgraph is zeroed when it is in contact with the work and the side knob assembly 210 is then moved until the indicator device shows the desired lateral movement of the work piece.

From the foregoing description, it will be seen that an improved center adjusting device is provided that fully accomplishes the aims and objects of the invention. It will be apparent to those skilled in the art that various modifications may be made in the form of the structures described with reference to the illustrated form of the invention without departing from the scope of the appended claims.

We claim:

1. In a machine having a headstock, a spindle mounted for rotation in said headstock and a Work holding member rotatable with said spindle; a center adjusting device comprising means mounting the work holding member in driven relation to the spindle including a plurality of members having cam surfaces mounted for rotation with the spindle and displaceable with respect to the axis of rotation of the spindle in any selected radial direction, means securing the Work holding member to said members having cam surfaces, cam followers adjustably supported by the headstock of the machine and upon adjustment thereof adapted to contact the members having cam surfaces and selectively move said members having cam surfaces radially of the axis of rotation of the spindle, and locking means securing said members having cam surfaces against radial movement relative to the axis of rotation of the spindle.

2. In a machine having a headstock, a spindle mounted for rotation in said headstock and a Work holding member rotatable with said spindle; a center adjusting device comprising means mounting the work holding member in driven relationship to the spindle including a plurality of members having cam surfaces mounted for rotation with the spindle and displaceable with respect to the axis of rotation of the spindle in any selected radial direction, means securing the Work holding member to said members having cam surfaces, cam followers adjustably supported by the headstock of the machine and upon adjustment thereof adapted to contact the members having cam surfaces and selectively move said member having cam surfaces radially of the axis of rotation of the spindle and adjustable friction means securing said members having cam surfaces against radial movement relative to the axis of rotation of the spindle.

3. In a machine having a headstock, a spindle mounted for rotation in said headstock and a work holding member rotatable with said spindle; a center adjusting device comprising means mounting said work holding member in driven relationship to the spindle including a pair of plates having cam surfaces thereon mounted for rotation with the spindle and displaceable with respect to the axis of rotation of the spindle in any selected radial direction, means securing the work holding member to said pair of members having cam surfaces, a pair of cam followers adjustably supported by the headstock of the machine and upon adjustment thereof adapted to contact the members having cam surfaces and selectively move their respective member of said pair of members having cam surfaces radially of the axis of rotation of the spindle, and locking means securing said pair of members having cam surfaces against radial movement relative to the axis of rotation of the spindle.

4. In a machine having a headstock, a spindle mounted for rotation in said headstock and a work holding member rotatable with said spindle; a center adjusting device comprising means mounting the work holding member in driven relationship to the spindle, including a pair of members having cam surfaces mounted for rotation with the spindle and displaceable with respect to the axis of rotation of the spindle in any selected radial direction, the cam surfaces of said pair of members being positioned eccentric to the axis of rotation of the spindle, means securing the work holding member to said pair of mem' bers having said cam surfaces, a pair of cam followers adjustably supported by the headstock of the machine and upon adjustment thereof adapted to contact the members having cam surfaces and selectively move said pair of members having cam surfaces radially of the axis of rotation of the spindle, and locking means securing said members having cam surfaces against radial movement relative to the axis of rotation of the spindle.

5. The invention defined in claim 4 wherein each of said members have paired cam surfaces with opposed cam peaks and the peaks of one of the members is displaced with respect to the peaks of the other of the members.

6. The invention defined in claim 5 wherein said pair of cam followers are circumferentially displaced 90 and are selectively movable toward and away from the axis of rotation of the spindle.

7. The invention defined in claim 4 wherein each of said pair of members has a pair of opposed cam surfaces with the surfaces thereof disposed generally eccentric to the axis of rotation of the spindle and each of the pair of cam surfaces of each of said pair of members is engageable by a cam lever.

8. In a machine having a headstock, a hollow spindle mounted for rotation in the headstock and a work holding member rotatable with said spindle; a center adjusting device comprising means mounting the work holding member in driven relationship to the hollow spindle including a plurality of members having cam surfaces mounted for rotation with the hollow spindle and displaceable with respect to the axis of rotation of the hollow spindle in any selected radial direction, means securing the work holding member to said members having cam surfaces, cam followers adjustably supported by the headstock of the machine and upon adjustment thereof adapted to contact the members having cam surfaces and selectively move said members having cam surfaces radially of the axis of rotation of the spindle, a draw bar extending through the opening in the hollow spindle, a draw bar nut threadedly engaging one end of the draw bar and adjustable into frictional engagement with one of said members having cam surfaces upon relative rotation of the draw bar with respect to the draw bar nut to secure the members having cam surfaces against radial movement realtive to the axis of rotation of the hollow spindle.

9. The invention defined in claim 8 including means cooperating with the hollow spindle and said members having cam surfaces and mounting said members for rotation with the hollow spindle and for limited radial movement relative to said hollow spindle.

References Cited in the file of this patent UNITED STATES PATENTS 1,751,772 Travis Mar. 25, 1930 2,423,312 Hamberger July 1, 1947 FOREIGN PATENTS 696,962 Germany Oct, 3, 1940