Chuck and method of chucking

A chuck and methods of chucking or clamping a workpiece for multiple machining operations without requiring rechucking or repositioning of the workpiece employs an arcuate cradle for supporting the workpiece with an abuttment at one of its ends. The workpiece is slid along the cradle until one of its ends is stopped by the abuttment, and then a jaw is pivoted against the other end of the workpiece to securely clamp the workpiece under hydraulic force derived from a machining tool to which the chuck is attached.

BACKGROUND OF THE INVENTION 
Our invention relates to the holding during machining operations of 
workpieces that include surfaces shaped like circular arcs, and more 
particularly to chucks and methods of clamping or chucking for circular 
arcuate workpieces that are less than 360 degrees in circumferential 
extent but that are not equal to 180 degrees. 
Simple mechanisms are available for holding workpieces that are circular, 
and workpieces that have portions that are circular arcs equal to 180 
degrees can be placed in an opposed mating relationship that permits them 
also to be held by simple mechanisms. However, when a workpiece 
essentially is shaped like a circular arc that is less than 360 degrees 
but is not equal to 180 degrees, such simple mechanisms can not be 
employed for accurate and close tolerance machining operations. In 
particular, when such a workpiece is a concave circular arcuate bearing 
that must be chucked for machining by rotation at high speed on a lathe, 
prior art chucks and methods of chucking are deficient. 
OBJECTIVES OF THE INVENTION 
Accordingly, it is an object of our invention to provide improved chucks 
and methods of chucking. 
Another object is to provide chucks and methods of chucking workpieces that 
are shaped like concave circular arc segments that are substantially less 
than 360 degrees in circumferential extent. 
Another object is to reduce machining down time by reducing the number of 
times a workpiece has to be re-chucked for multiple machining operations. 
Another object is to provide hydraulically actuated chucks for holding 
circular arcuate workpieces during mass production operations that are 
fast acting and employ direct positive gripping forces. 
Another object is to provide chucks and methods of chucking that permit 
several machining operations to be performed on a workpiece without 
requiring that the workpiece be positioned or rechucked. 
Another object is to provide chucks that do not bend or distort circular 
arcuate workpieces. 
Another object is to provide chucks that expose for machining the opposite 
surfaces of a workpiece shaped like a circular arc segment. 
Another object is to provide chucks and methods of chucking circular arc 
bearing segments for machining on lathes or on machining centers. 
Another object is to provide chucks that clamp a bearing half segment in 
one chucking operation that enable the bearing segment to be accurately 
located for boring, to have opposed circumferential edges chamfered, to 
have an oil groove machined in its concave surface, and to have oil access 
holes bored in it, without having to adjust or rechuck the bearing 
segment. 
Another object is to provide relatively simple and low cost, durable, 
easily maintained, accurate chucks and chucking methods that can be used 
for righthand or lefthand high speed machining operations and which do not 
possess defects found in similar prior art devices and methods. 
Another object is to provide a chuck jaw for securely clamping the ends of 
an arcuate workpiece even though such ends may be irregular or misaligned. 
Other objects and advantages of our invention will be found in the 
specification and claims, and the scope of the invention will be set forth 
in the claims.

DESCRIPTION OF THE INVENTION 
The drawing shows a chuck 1 in accord with our invention for holding a 
workpiece 2 during a machining operation on a machine tool, such as a 
conventional lathe having a spindle 3. As shown in the drawing, workpiece 
2 is an automative bearing half which is shaped like a segment of a 
circular arc that is substantially less than 360 degrees. Workpiece 2 may 
include a flange 4 on each side and the workpiece has a concave surface 5 
and a convex surface 6. The workpiece has a circumferential arcuate length 
or extent slightly greater than 180 degrees, which permits its ends to be 
machined down during a final operation to a final predetermined 
circumferential length and that may be closer to or less than 180 degrees. 
Convex surface 6 is supported by the mating concave circular arcuate 
surface 7 of a chuck cradle portion 8, and the flanges 4 overlap the edges 
on each side of the cradle. Cradle portion 8 is part of a removable jaw 
assembly 9 that is attached to chuck body 10 by bolts 11, and jaw 9 may be 
removed and replaced by other jaws having different cradle portions 
dimensioned to mate with similar but differently dimensioned workpieces. A 
stop member 12 is attached at one end 13 of cradle portion 8 by bolts 15 
and has a rotatable or pivoting pad 16 for abutting against one end 17 of 
the workpiece when the workpiece is supported by arcuate surface 7. The 
inner end 19 of stop member 12 extends generally radially of arcuate 
surface 7 toward the central axis 20 of the chuck. A pivotable jaw 22 
adjacent the other end 23 of cradle portion 8 clamps against the other end 
24 of the workpiece when the workpiece is supported by arcuate surface 7. 
Jaw 22 also has a rotatable or pivoting pad 21 for contacting end 24, and 
pads 16 and 21 accomodate irregularities and misalignment in workpiece 
ends 17 and 24. 
A center bore 25 extends completely through chuck body 10, and at one end 
of body 10, bore 25 is enlarged to define a circular groove 26 adjacent 
arcuate surface 7. Groove 26 has a larger diameter than both arcuate 
surface 7 and workpiece 2 for receiving cradle 8. One edge 28 of the 
workpiece extends beyond the terminal edge 29 of the chuck while the 
opposite edge 30 of the workpiece extends beyond arcuate surface 7 into a 
circular chamber 27 that has a diameter smaller than groove 26 but larger 
than bore 25. This exposes the opposite edges 28 and 30 of the workpiece 
for machining operations. The central axes of bore 25, arcuate surface 7, 
and workpiece surfaces 5 and 6 are all coincident with central axis 20. 
Workpiece 2 may have a projecting portion such as tang 31, and there is a 
slot 32 in arcuate surface 7 for receiving such a projecting portion. 
The means for moving or pivoting jaw 22 includes cylindrical hollow 
actuator means 35 that is centered in bore 25 and that slides axially in 
bore 25 along axis 20 as indicated in phantom at 33 in FIG. 2. Actuator 35 
has a pair of identical opposed arms 36 that merge with a coaxial 
cylindrical ridge 38 on the outside of the actuator. Arms 36 and ridge 38 
extend perpendicularly to bore 25 into a cavity 39 in body 10 that 
communicates with bore 25. Shafts 37 are held in arms 36, and each shaft 
supports a pair of identical cylindrical cam rollers 40 that are separated 
by a spacer. Pivotable jaw 22 is connected to one end 41 of rotatable 
shaft means 42 by a bolt 43, and shaft 42 is journaled in sleeve bearings 
45 in a cylindrical hole 46 in body 10 that has its axis 47 parallel to 
axis 20. Shaft means 42 and jaw 22 are keyed to each other at 44. At an 
intermediate portion 48 of shaft 42 a pair of enlarged identical helical 
cam surfaces 49 mate with roller cams 40. Axial movement of actuator 35 in 
bore 25 and cavity 39, as indicated by arrow 50, causes cam rollers 40 to 
move along helical surfaces 49 and such movement rotates shaft 42 around 
axis 47. Rotation of shaft 42 causes jaw 22 to pivot with respect to axis 
47. 
Cylindrical end 51 of actuator 35 may be bolted to or threaded on to the 
threaded end 52 of a conventional hydraulically actuated cylindrical 
drawtube or drawbar 53 of a conventional lathe. Axial movement of drawbar 
53 provides hydraulic force in the range of about 2,000-3,000 pounds for 
moving actuator 35, and the hydraulic force on drawbar 53 provides the 
force for holding the chuck parts and the workpiece 2 in place during the 
machining operations. As shown in FIG. 1, jaw 22 has been pivoted into 
contact with end 24 of workpiece 2. When workpiece 2 is to be removed from 
chuck 1, drawbar 53 advances actuator 35 axially along axis 20 toward the 
workpiece as indicated in phantom at 33. This movement rolls cams 40 along 
helical surfaces 49, which causes shaft 42 to pivot counterclockwise and 
move jaw 22 out of contact with the workpiece. In like manner, retraction 
of drawbar 53 toward the position shown in FIG. 1 moves actuator 35 away 
from the workpiece, and such movement rolls cams 40 over helical surfaces 
49, and this movement rotates shaft 42 clockwise and pivots jaw 22 into 
contact with the workpiece as shown. Edge 54 of cavity 39 defines an 
abutment for limiting movement of actuator 35 by contact with ridge 38. 
The other end 55 of shaft 42 is journaled for rotation in a bearing 56 
fitted into a cavity 57 in an end plate 58 of chuck 1. End plate 58 is 
attached to body 10 by bolts 59. Chuck 1 may be held on a lathe by a 
spindle adapter 60 that is attached to body 10 by bolts 61. Suitable bolts 
that pass through bolt holes such as 62 that are aligned with mating holes 
on the lathe spindle 3 in conventional manner secure spindle adapter 60 to 
the lathe. Suitable gasketing such as at 63 may be provided to help retain 
lubricating fluids, and cradle portion 8 may have suitably located holes 
such as 64 for enabling machine tools to drill holes or slots such as oil 
access hole 65 in the workpiece. 
Pads 16 and 21 may be identical, and, as shown in FIGS. 4 and 5, each pad 
has on one side a flat surface 68 for contacting an end 17 or 24 of the 
workpiece. A semicircular hump 69 on the opposite side of each pad fits 
into a mating semicircular groove 70 in an end of stop member 12 and 
pivotable jaw 22. Groove 70 provides a bearing surface supporting the 
mating surface of hump 69. A cylindrical shoulder bolt 71 defines shaft 
means that passes through a center hole in each pad, and bolt 71 threads 
into a tapped hole 72 in member 12 and jaw 22 for attaching the pads 16 
and 21. Sufficient clearance is provided at 73 to permit rotation or 
pivoting of the pads. The top side of stop member 12 contacts an abuttment 
75 that is attached to chuck body 10 by bolt 76. Abuttment 75 prevents 
movement or rotation of jaw assembly 9 when clamping force is applied to 
the workpiece 2 by pivoting jaw 22. 
A locator clip 77 is held in a recess 78 in cradle portion 8. Recess 78 
merges into groove 32, and the clip is held in place by a bolt 79 threaded 
into a tapped hole in the side of the clip. An integral spring arm 80 of 
clip 77 extends from recess 78 into contact with tang 31. An edge of arm 
80 defines an edge of slot 32 in order to locate and hold workpiece 2 in 
its proper position for machining. 
Our invention also includes methods for holding a circular arcuate 
workpiece 2 during machining operations on a lathe having a spindle 3. To 
load the workpiece into chuck 1, the workpiece is first placed in cradle 8 
with its end 17 spaced from fixed jaw 12, as indicated at 66 in FIG. 1, 
and its convex surface 6 supported on concave surface 7 of the cradle. At 
this time jaw 22 would be pivoted to its open position as indicated in 
phantom in FIG. 1. Then while its surface 6 is supported on concave 
surface 7, workpiece 2 is slid along cradle 8 until one end 17 contacts an 
abuttment defined by pad 16. Workpiece 2 is then clamped securely in chuck 
1 by exerting a clamping force on its ends by pivoting jaw 22 against the 
other end 24 of the workpiece. The clamping force may be a hydraulic force 
or pressure from drawbar 53. 
It has thus been shown that by the practice of our invention a workpiece 2 
may be a bearing half segment that is stably and securely held in a chuck 
1 by a relatively simple mechanism using the conventional drawbar 53 of a 
lathe to move circular cam rollers 40 over helical surfaces 49 and thereby 
clamp the workpiece ends 17 and 24 between a stop member 12 and a pivoting 
jaw 22 of a removable jaw 9. This permits opposed edges 28 and 30 of the 
bearing to be exposed for machining and chamfering by extending edge 28 
past the terminal edge 29 of the chuck and extending edge 30 past an edge 
of cradle portion 8 into chamaber 27. An oil groove 67 may be machined in 
concave surface 5 of bearing workpiece 2 and oil entry hole 65 may be 
drilled in the bearing without requiring that the workpiece be rechucked 
or repositioned in the chuck. When a workpiece of different size or shape 
is to be machined, it is only necessary to remove bolts 11 and replace jaw 
9 with another jaw 9 having a cradle portion 8 with a suitably shaped 
surface 7 for supporting the new workpiece and an appropriately spaced 
stop member 12 and pivoted jaw 22. In the practice of our methods, the 
steps of sliding the workpiece along the supporting surface 7 until one 
end 17 is stopped by abuttment with fixed jaw 12 and tang 31, and/or 
flange 4, are in place, and then exerting a hydraulic clamping force 
against the other end 24 assures that the workpiece is accurately and 
securely held in place while it is rotated at high speed on a lathe as 
well as during other types of machining operations. Floating pads 16 and 
21 assure that workpiece 2 is securely clamped in the chuck even though 
its ends 17 and 24 may be misaligned or uneven, and an edge of spring arm 
80 of locator clip 77 pushes against tang 31 in slot 32 and assures 
accurate alignment of the workpiece for precise machining operations. 
While our invention has been described with reference to a particular 
embodiment, it is not intended to illustrate or describe herein all of the 
equivalent forms or ramifications thereof. For example, workpiece 2 has 
been illustrated as being just slightly greater than 180 degrees in 
circumferential extent, but the workpiece held by our chuck could also be 
significantly greater than or slightly or significantly less than 180 
degrees in circumferential length. Also, the words used are words of 
description rather than limitation, and various changes may be made 
without departing from the spirit or scope of the invention we have 
disclosed herein. We intend that the appended claims cover all such 
changes as fall within the true spirit and scope of our invention.