Apparatus for supporting a workpiece

A method and apparatus for rotatably supporting a workpiece WP includes a bearing ring 300 which extends around a center support member 204. The bearing ring is deflectable inwardly at a plurality of spaced apart locations 310 to engage the center support member at these locations during machining of a workpiece. At each of the locations where the bearing ring is deflected inwardly into engagement with the center support member, the bearing ring has a reduced thickness to thereby reduce the resistance of the bearing ring to deformation at these locations. Fluid pressure applied against the outside of the bearing ring deflects the bearing ring inwardly at the locations of reduced thickness. The deflected portions of the bearing ring engage the center support member to securely hold it during machining of a workpiece. When the machining of a workpiece is finished, the fluid pressure against the bearing ring is reduced and the natural resilience of the bearing ring causes it to return to its original configuration.

This invention relates to an for supporting a workpiece for rotation about 
an axis during machining of the workpiece. 
Known machine tools have a tailstock to support a workpiece during 
machining of the workpiece. These known tailstocks have a center which is 
supported by a quill or center support member. The center is movable along 
the axis of rotation of the workpiece by a motor connected with the quill. 
A cylindrical bearing ring or bushing is provided around the quill to 
support the quill for axial movement. During machining of the workpiece, 
force is transmitted from the quill through the bearing ring to a 
tailstock housing or frame. A clearance space is provided between the 
outside of the quill and the inside of the bearing ring to accommodate 
axial movement of the quill relative to the bearing ring. This clearance 
space allows sidewise movement of the tailstock center to occur under the 
influence of forces transmitted from the quill to the bearing ring during 
machining of a workpiece. One example of a tailstock having such a 
construction is shown in U.S. Pat. No. 3,160,041 issued Dec. 8, 1964 and 
entitled Tailstock. Other known tailstocks for supporting a workpiece are 
disclosed in U.S. Pat. No. 2,614,447 issued Oct. 21, 1952 and entitled 
Tailstock and in U.S. Pat. No. 3,533,316 issued Oct. 13, 1970 and entitled 
Hydrostatic Precision Tailstocks. 
SUMMARY OF THE INVENTION 
The present invention relates to a new and improved apparatus for 
supporting a workpiece for rotation during machining of the workpiece. A 
center is provided to engage one end of the workpiece. A support member 
for the center is movable along the axis of rotation of the workpiece to 
move the center into engagement with one end of the workpiece. A bearing 
ring extends around the support member. 
In accordance with a feature of the invention, the bearing ring is 
deflected inwardly at a plurality of spaced apart locations to grip the 
center support member during machining of the workpiece. This inward 
deflection of the bearing ring eliminates the clearance space between the 
bearing ring and the center support member. The bearing ring may be 
deflected inwardly by fluid pressure applied to the outer side surface of 
the bearing ring. Deflection of the bearing ring at selected locations is 
promoted by reducing the cross sectional area of the bearing ring at these 
locations to thereby reduce the resistance of the bearing ring to elastic 
deformation under the influence of fluid pressure.

Referring now to the drawings, a machine tool 10 is schematically 
illustrated in FIG. 1. The machine tool 10 has a headstock (not shown) 
enclosed within a housing 11. The headstock is engageable with one end of 
a workpiece WP to support the workpiece for rotation about a horizontal 
central axis A. A tailstock assembly 200 engages the opposite end of the 
workpiece to further support the workpiece for rotation about the axis A. 
A pair of turrets 12 and 13 are rotatable about horizontal axes extending 
parallel to the axis A. The turrets 12 and 13 are mounted on slides 14 and 
15 for movement along the axis A and for movement toward and away from the 
workpiece WP. The turrets 12 and 13 hold known cutting tools 16 
(illustrated schematically in FIG. 1) for cutting metal from the workpiece 
WP during rotation of the workpiece about the axis A. Operation of the 
machine tool 10 is regulated by controls 17. 
During operation of the machine tool 10, a slidable housing panel 18 is 
closed to enclose a work area in which the tools 16 cut metal from the 
workpiece WP. The illustrated machine tool 10 has a slant bed or base 19. 
The machine tool 10 is commercially available from the Warner & Swasey 
Company, Turning Division of 31700 Solon Road, Solon, Ohio, U.S.A., under 
the designation TITAN (Trademark) Slant Bed Universal. However, the 
machine tool 10 could have other known constructions and the present 
invention is not to be limited to any specific type of machine tool. 
The construction of the tailstock assembly 200 is illustrated in FIG. 2. 
The tailstock assembly 200 includes a center 201 having a conical outer 
end portion 202 which engages one end of a workpiece WP to rotatably 
support the workpiece during operation of the machine tool 10. The center 
201 is fixedly connected to a spindle 203. The center 201 and spindle 203 
have central axes which are coincident with the axis A of rotation of the 
workpiece WP. 
The spindle 203 is rotatably supported in a quill or center support member 
204 by bearings 205 and 206. The bearings 205 are capable of withstanding 
both radial and axial load forces. The bearing 206 is primarily capable of 
withstanding radial load forces. The cylindrical quill or center support 
member 204 is mounted in a tailstock housing 208 with its central axis 
coincident with the axis A about which the workpiece WP is rotated by the 
headstock. The center support member 204 is axially movable along the 
slant bed 19 (FIG. 1) of the machine tool 10 to position the center 201 
adjacent to one end of the workpiece WP. 
A hydraulic piston and cylinder type motor 210 (FIG. 2) is connected with 
one end of the center support member 204. The motor 210 is operable to 
move the center support member 204 along the axis A toward and away from 
the workpiece WP. This movement of the center support member 204 by the 
motor 210 moves the end 202 of the center 201 into engagement with the end 
of the workpiece WP to rotatably support the one end of the workpiece in a 
known manner. The motor 210 has a piston rod 211 connected with one end of 
the center support member 204. A rod 212 extends from the tailstock 
housing 208 into an opening 213 in the center support member 204 to hold 
the center support member against rotation about the axis A. 
A detector assembly 215 is connected with the center support member 204 and 
provides an output signal which indicates whether the center support 
member and center 201 are in the retracted position shown in FIGURE 2 or a 
fully extended position to the left of the position shown in FIG. 2. The 
detector assembly 214 includes a first proximity switch 216 which is 
actuated by a circular head end 217 of a rod 218 connected to the center 
support member 204 when the center support member is in the retracted 
position of FIG. 2. When the center support member 204 has been moved to 
the fully extended position by operation of the motor 210, the head end 
217 and the rod 218 is adjacent to and causes actuation of a second 
proximity switch 219. 
A pair of identical bearing rings 200 and 400, constructed in accordance 
with a feature of the present invention, support the quill or member 204 
for axial movement relative to the housing 208. Thus, when the motor 210 
is operated to extend the piston rod 211, the center support member 204 is 
moved toward the left (as viewed in FIG. 2). As this occurs, a cylindrical 
outer side surface 221 of the center support member 204 slides along 
cylindrical inner side surfaces 301 and 401 of the annular bearing rings 
300 and 400. Although it is preferred to construct the center support 
member 204 and bearing rings 300 and 400 with circular cross sectional 
configurations, the center support member and bearing rings could have 
noncircular cross sectional configurations if desired. 
If the motor 210 is operated to move the center support member 204 to a 
fully extended position, the head end 217 on the detector rod 218 will 
actuate the proximity switch 219 to cause the turning machine controls 17 
(FIG. 1) to interrupt operation of the machine tool 10. However, it is 
contemplated that the leading or outer end 202 (FIG. 2) of the center 201 
will engage the end of the workpiece WP before the center support member 
is moved to a ully extended position. The center 201 is moved out of 
engagement with the end of a workpiece WP by reversing a direction of 
operation of the motor to move the center support member 204 toward the 
right (as viewed in FIG. 2). 
The bearing rings 300 and 400 have an interference fit with the housing 208 
to hold them against axial movement with the center support member during 
operation of the motor 210. A pair of parallel pins 223 and 224 extend 
from a housing 208 into engagement with notches 302 and 402 formed in 
axial ends of the bearing rings 300 and 400. The pins 223 and 224 hold the 
bearing rings in a predetermined angular orientation with the housing 208. 
During axial movement of the center support member 204, friction forces are 
transmitted between the cylindrical outer side surface 221 of the center 
support member and the cylindrical inner side surfaces 301 and 401 of the 
bearing rings 300 and 400. These friction forces are minimized by 
providing a lubricating liquid in an annular chamber 225 disposed between 
the center support member 204, housing 208 and axial ends of the bearing 
rings 300 and 400. 
In addition to providing lubricating liquid in the chamber 225 to minimize 
friction forces, a clearance space of 0.0254 mm. to 0.0381 mm. is provided 
between the outer side surface 221 of the center support member 204 and 
the inner side surfaces 301 and 401 of the bearing rings 300 and 400. If a 
smaller clearance space is left between the outer side surface 221 of the 
center support member 204 and the inner side surfaces 301 and 401 of the 
bearing rings 300 and 400, frictional forces will tend to effectively lock 
up the center support member 204. The clearance space is also necessary to 
allow for thermal expansion of either the bearing rings 300 and 400 or the 
center support member 204. 
If the clearance space between the outer side surface 221 of the center 
support member and the inner side surfaces 301 and 401 of the bearing 
rings 300 and 400 is not eliminated before machining of the workpiece WP 
begins, the center support member 204 will move relative the bearings 300 
and 400 and housing 208 during machining of the workpiece WP. Thus, the 
center support member 204 will tend to move relative to the bearings 300 
and 400 when the direction in which cutting forces are applied to the 
workpiece changes. The center support member 204 will also tend to move 
during machining of the workpiece WP if the workpiece is not balanced 
about the axis A. 
In accordance with a feature of the invention, the bearing rings 300 and 
400 (FIG. 2) are deflectable inwardly to eliminate the clearance space 
between the outer side surface 221 of the center support member 204 and 
the inner side surfaces 301 and 401 of the bearing rings 300 and 400 
during machining of the workpiece WP. In the illustrated embodiment of the 
invention, the bearing rings 300 and 400 are elastically deflected 
inwardly by fluid pressure to engage the outer side surface 221 of the 
center support member 204. Thus, high pressure hydraulic fluid from a pump 
227 is conducted through a control valve 228, conduits 229 and passages 
230 and 231 formed in the housing 208 to annular pressure distribution 
rings 232 and 233 (FIG. 2). 
The pressure distribution rings 232 and 233 are formed in the tailstock 
housing 208 and extend around the bearing 300 and 400. The pressure 
distribution rings 232 and 233 open radially inwardly toward outer side 
surfaces of the bearing rings 300 and 400. The fluid pressure conducted 
from the pump 227 to the pressure distribution rings 232 and 233 is 
applied against the outside of the bearing rings 300 and 400 throughout 
the circumference of the bearing rings. In one specific instance, the 
bearing rings 300 and 400 were exposed to and elastically deflected 
radially inwardly into engagement with the center support member 204 by a 
hydraulic fluid pressure of approximately 800 psi. Of course, the specific 
fluid pressure applied against the outside of the bearing rings 300 and 
400 will depend upon the force required to deflect the bearing rings and 
the force to be applied against the center support member 204 to hold the 
center support member during machining of the workpiece. 
When the center support member 204 is to be moved axially relative to the 
housing 208 by the motor 210, the machine tool controls 17 effect 
operation of the valve 228 to connect the conduit 229 in fluid 
communication with drain or reservoir 235. The resulting reduction in the 
fluid pressure in the distribution rings 232 and 233 allows the natural 
resilience of the bearing rings 300 and 400 to cause them to spring back 
to their original configuration. This results in the reestablishing of the 
clearance space between the bearing rings 300 and 400 and the center 
support member 204. 
The machine tool controls 17 then effect operation of the motor 210 to move 
the center support member 204 to position the center 210 at a desired 
location along the axis A. The valve 228 is then actuated back to the 
position shown in FIG. 2 to again deflect the bearing rings 300 and 400 
into engagement with the center support member 204. In the illustrated 
machine tool 10, the workpiece WP is supported by a tailstock assembly 
200. However, it is contemplated that the bearing rings 300 and 400 could 
be used in workpiece support assemblies other than the tailstock assembly 
200. 
The relationship between the bearing ring 300, the center support member 
204 and the housing 208 is further illustrated in FIG. 3. The annular 
pressure distribution ring 232 formed in the housing 208 is connected in 
fluid communication with the passage 230. The pressure distribution ring 
opens inwardly and cooperates with the bearing ring 300 and surfaces of 
the housing 208 to form a pressure pocket 237. The fluid pressure 
communicated to the pressure pocket 237 is effective to elastically 
deflect the bearing ring 300 inwardly against the outer side surface 221 
of the center support member 204. This deflection of the bearing ring 300 
occurs without plastic, that is, permanent, deformation of the bearing 
ring. 
O-ring seals 304 and 305 are disposed in annular recesses 306 and 307 
formed in the bearing ring 300. The circular O-ring seals 304 and 305 
sealingly engage a cylindrical inner side surface 239 of the housing 208 
at locations on axially opposite sides of the pressure distribution ring 
232. The seals 304 and 305 prevent fluid leakage axially along the one 
piece bearing ring 300. The pin 223 extends into the notch 302 to hold the 
bearing ring 300 against axial movement toward the right (as viewed in 
FIG. 3), to locate the bearing ring circumferentially relative to the 
center support member 204 and the housing 208 and to hold the bearing ring 
300 against rotation relative to the housing 208. 
The construction of the bearing ring 300 is further illustrated in FIG. 4. 
The one piece bearing ring 300 has a cylindrical outer side surface 309 in 
which a plurality of flats 310 are formed. The flats 310 reduce the 
thickness of the bearing ring 300 at spaced apart locations around the 
circumference of the bearing ring. The reduced thickness of the bearing 
ring 300 at the flats 310 reduces the structural stiffness of the bearing 
ring to enable it to be deflected radially inwardly by pressure applied 
against the flats 310. 
The flats 310 are connected in fluid communication by arcuate segments 312 
of an annular groove. The arcuate groove segments 312 are radially aligned 
with the pressure distribution ring 232 (FIG. 3). The groove segments 312 
conduct fluid pressure around the cylindrical bearing ring 300 between the 
flats 310. 
At locations other than the flats 310, the bearing ring 300 has sufficient 
structural stiffness to resist deflection under the influence of the fluid 
pressure forces applied against the outside of the bearing ring. 
Therefore, the bearing ring 300 is deflected radially inwardly into 
engagement with the center support member 204 only at the flats 310. 
FIG. 5 illustrates the manner in which the flats 310 are arranged on the 
bearing ring 300 and are interconnected by the arcuate groove segments 
312. The flats 310 are cut into the side of the cylindrical bearing ring 
300 as chords. This results in the side wall of the bearing ring 300 
having a circumferentially tapered cross sectional configuration at each 
of the flats 310. The cross sectional area of the bearing ring 300 is 
greater in a radial plane extending from the axis A through the bearing 
ring at a location circumferentially offset from the flats 310 than in a 
radial plane extending through a central portion of one of the flats. 
The side wall of the bearing ring 300 tapers circumferentially from a 
relatively thick cross section where each of the flats 310 intersects the 
outer side surface 309 of the bearing ring to a relatively thin cross 
section at the center of a flat. Thus, the bearing ring 300 is relatively 
thick at axially extending edges 314 and 315 of each of the flats 310. The 
bearing ring 310 is relatively thin at a central portion 316 of each of 
the flats 310. The circumferentially tapered cross sectional configuration 
of the bearing ring at the flats 310 enables the bearing ring 300 to have 
a relatively long service life since there are no stress concentrations or 
corners to cause fatigue failure upon repeated deflecting of the bearing 
ring. 
Although the one piece bearing ring 300 has four flats 310 in the 
embodiment of the invention illustrated in FIG. 5, it is contemplated that 
greater or lesser number of flats 310 could be provided if desired. Thus, 
the bearing ring 300 could be provided with three flats 310 or five flats 
310. However, it is preferred to form the bearing ring 300 with four flats 
310 at equally spaced locations about the circumference of the bearing 
ring. 
The size of the bearing ring 300 will depend upon the size of the center 
support member 204 with which the bearing ring is used. However, in one 
specific embodiment of the bearing ring, the cylindrical outside surface 
309 of the bearing ring has a diameter of approximately 150 mm. The 
cylindrical inside surface 301 of the bearing ring had a diameter of 
approximately 140 mm. Therefore, the wall of the bearing ring, at 
locations other than the flats and the grooves 306, 307 and 312, had a 
thickness of 5 mm. 
In this illustrative embodiment of the bearing ring 300, the minimum 
thickness of the bearing ring wall at the center 316 of each of the flats 
310 was approximately 4 mm. The arcuate groove segments 312 had a depth of 
0.8 mm. The flats 310 had an arcuate extent of approximately 26 degrees 
and 32 minutes with a resulting circumferential extent or distance between 
parallel edges 314 and 315 of approximately 32.5 mm. This particular 
bearing ring 300 had an axial extent of approximately 100 mm and each of 
the flats 310 had an axial extent of approximately 50 mm. The specific 
bearing ring 300 having the foregoing dimensions was made of a cast 
manganese bronze (SAE 430B) to provide a relatively low coefficient of 
sliding friction between the bearing support member 204 and the bearing 
300. 
It should be understood that the foregoing dimensions and material of the 
bearing ring 300 have merely been set forth for purposes of clarity of 
description and not for purposes of limitation of the invention. Thus, it 
is contemplated that the bearing ring 300 could be formed with different 
dimensions and of different materials. It is also contemplated that the 
bearing ring 300 could have a cross sectional configuration other than the 
illustrated circular cross sectional configuration. In addition, the flats 
310 could be formed with a different configuration. For example, each of 
the flats 310 could be formed with an arcuate configuration with a center 
which is either coincident with the center of the bearing ring 300 or with 
a center which is located outside of the bearing ring. 
The manner in which the bearing ring 300 is deflected inwardly at a 
plurality of space apart locations to engage the center support member 204 
during machining of a workpiece WP is illustrated schematically in FIG. 6. 
The fluid pressure conducted to the pressure distribution ring 232 through 
the passage 230 is applied against the outside of the bearing ring 300. 
Due to the reduced thickness of the bearing ring 300 at the flats 310 with 
a resulting reduced resistance to elastic deformation, the bearing ring 
300 is deflected radially inwardly at the flats 310. The distance which 
the bearing ring 300 is deflected inwardly at each of the flats 310 
corresponds to the clearance between the inner side surface 310 of the 
bearing ring 300 and the outer side surface 221 of the center support 
member 204, that is, approximately 0.03 mm. 
When the flats 310 are deflected inwardly by the fluid pressure in the 
pockets 237 between the flats and the inner side surface 232 of the 
housing 208, the circumferentially tapered cross sectional configuration 
of the bearing ring 300 at the flats (FIG. 5) results in substantially 
line contact between the inside surface 301 of the bearing ring with the 
outside surface 221 of the center support member at each of the flats 310. 
The portions of the bearing ring 300 between the flats 310 remain 
substantially undeflected so that the clearance space remains between 
these portions of the bearing ring 300 and the center support member 204. 
It should be understood that FIG. 6 is merely a schematic illustration of 
the manner in which the bearing ring 300 is deflected at the flats 310 and 
that the actual deflection will be substantially less than illustrated in 
FIG. 6. Although only the bearing ring 300 has been illustrated in FIGS. 
3-6, the bearing ring 300 has the same construction as the bearing ring 
400 and is deflected in the same manner as the bearing ring 300. Although 
it is preferred to apply fluid pressure against each of the flats 310 to 
deflect the bearing ring 300, it is contemplated that pressure could be 
applied against the flats 310 in a different manner. For example, 
hydraulically actuated plungers could be pressed against the flats 310 to 
force them inwardly. 
FIG. 7 is a highly schematicized illustration depicting the relationship 
between the bearing ring 300, the workpiece WP and the slant bed 19 of the 
machine tool 10. The resultant of the various forces transmitted during 
machining of the workpiece WP is indicated schematically by the dashed 
arrow R in FIG. 7. The resultant machining force R is opposed by reaction 
forces RF at a pair of deflected flats 310 on the bearing ring 300 and a 
corresponding pair of deflected flats on the bearing ring 400. Since the 
resultant machining force R is opposed by reaction forces RF at a pair of 
flats on each of the bearing rings 300 and 400, the reaction forces RF are 
not excessively large. 
During a machining operation, a tool 16 presses radially inwardly against 
the workpiece WP so that a tool force TF is transmitted from the workpiece 
WP to the center support member 204. In addition, the formation of a chip 
C at the cutting tool 16 results in the transmittal of a cutting force CF 
to the tailstock support member 204. The resultant cutting force RCF is 
indicated schematically in FIG. 7. In addition to the foregoing forces 
resulting from the use of the cutting tool 16, there is a downward force W 
due to the weight of the workpiece. 
The resultant machining force R is directed approximately midway between 
the deflected flats 310 disposed on the left (as viewed in FIG. 7) half of 
the bearing ring 300. The reaction forces RF are disposed above and below 
the line of action of the resultant machining force R and are spaced apart 
by less than 180.degree. about the axis of rotation A of the workpiece WP. 
The reaction forces RF have lines of action which intersect at the central 
axis A of the workpiece WP. 
The foregoing analysis assumes that the workpiece WP is rotating in a 
counterclockwise direction, as indicated by the arrow B in FIG. 7. Of 
course, if the direction of rotation of the workpiece WP was reversed, the 
resultant force would be directed between a different pair of cutting 
flats 310. The illustrated cutting tool 16 is disposed on the lower turret 
13 (FIG. 1). If a cutting tool on the upper turret 12 was used, the 
resultant force R would also be directed between a different pair of flats 
310. 
Regardless of which turret 12 or 13 the cutting tool 16 being used is 
mounted and regardless of the direction of rotation of the workpiece, the 
resultant force is advantageously transmitted between a pair of adjacent 
flats 310 to minimize the reaction forces RF which must be transmitted 
between the center support member 204 and the bearing ring 300 at any one 
of the flats. It should be understood that the specific magnitude of the 
resultant force R will vary depending upon the magnitude of the tool force 
TF, cutting force CF and the weight of the workpiece WP. 
OPERATION 
When a machining operation is to be undertaken on a workpiece WP with a 
machine tool 10, the workpiece is first mounted in a headstock chuck (not 
shown). The tailstock frame or housing 208 is then moved along the bed 19 
in a direction parallel to the axis A until the center 201 (FIG. 2) is 
adjacent to one end of the workpiece WP. At this time, the valve 228 
connects the conduit 229 with the drain 235 so that the bearing rings 300 
and 400 are in an undeflected or relaxed initial condition. 
The controls 17 then effect operation of the motor 210 to move the center 
support member 204 toward the left (as viewed in FIG. 2). When the leading 
or outer end 202 of the center 201 engages the end of the workpiece WP, 
operation of the motor 210 is stopped. Fluid pressure in the motor 210 
holds the center 201 against the workpiece with a desired axial loading 
force. 
In order to eliminate the clearance between the center support member 204 
and the housing 208, the controls 17 move the valve 228 to the position 
shown in FIG. 2 connecting the conduit 229 with the pump 227. Hydraulic 
fluid pressure from the pump 227 is conducted to the pressure distribution 
rings 232 and 233. This fluid pressure is applied against the outside of 
the bearing rings 300 and 400. The bearing rings 300 and 400 are 
elastically deflected radially inwardly at a plurality of locations to 
securely grip the outer side surface 221 of the center support member 204. 
The fluid pressure against the outside of the bearing ring 300 deflects the 
bearing ring inwardly at a plurality of locations, that is, at the flats 
310, in the manner illustrated schematically in FIG. 6. When the bearing 
rings 300 and 400 have the specific dimensions and are formed of the 
material previously set forth herein, a fluid pressure of approximately 
800 psi will deflect the bearing rings 300 and 400 and cause them to 
firmly grip the center support member 204. Although deflection of only the 
bearing ring 300 has been illustrated in FIG. 6, it should be understood 
that the bearing ring 400 has the same construction as the bearing ring 
300 and is deflected inwardly in the same manner as the bearing ring 300. 
The deflected bearing rings 300 and 400 securely grip the center support 
member 204 to hold the center support member against movement during 
machining of the workpiece WP. Thus, the resultant force R generated 
during machining of the workpiece WP (FIG. 7) is transmitted through the 
bearing rings 300 and 400 to the tailstock housing 208. The deflected 
bearing rings 300 and 400 hold the center support member 204 against 
movement during the machining operation. Therefore, a workpiece WP can be 
accurately machined to a desired configuration. 
When the machining operation on the workpiece WP has been completed, the 
control 17 actuates the valve 228 to connect a conduit 229 with a drain or 
reservoir 235. A resulting reduction in the fluid pressure applied against 
the bearing rings 300 and 400 allows the natural resilience of the bearing 
rings to cause them to spring back to their initial configuration. This 
establishes clearance space between the center support member 204 and the 
bearing rings 300 and 400 to enable the center support member to be 
readily moved by the motor 210. Once the machining operations have been 
completed, the motor 210 will be operated to move the center support 
member 204 toward the right (as viewed in FIG. 2) to disengage the center 
201 from the workpiece.