Background of the invention This invention relates to surfacing machines. Surfacing machines which are mounted within a workpiece, such as a large valve or the like, typically cannot accurately repeat a given mount. This is critical when the operator must mount and dismount the machine to change surfacing tools in the course of a surfacing operation because of an inability to access a tool head disposed deep with¬ in the workpiece. Initially, the machine is mounted and aligned relative to a portion of the workpiece to be surfaced and a cutting operation is performed. The machine is then dismounted in order to attach a grinding tool and is remounted, as close to the initial mount as possible, to perform a grinding operation. Misalignment relative to the initial mount requires that the grinding operation first work the surface to conform to the new mounting alignment and the net result is that an excessive amount of material is removed due to the misalignment. Many prior art devices require special mounting surfaces integral to the workpiece, i.e. the valve body, and are often limited to special surfacing operations, such as valve seat resurfacing.

Summary of the Invention A surfacing machine utilizing a central tubu¬ lar turning bar having a tool support arm mountable on the bar and a drive mechanism mounted on the bar provides improved visual and physical access to a work site at the interior of a workpiece, such as a valve body, when the surfacing machine is mounted

within the workpiece. Hoses and control rods are routed through the tubular turning bar to the tool head to provide power to and radial positioning of various tool heads mountable on the tool support arm. Support chucks are mountable to the workpiece and include bearing elements which ride directly on the exterior surface of the turning bar and allow ^" for rotational and axial movement of the turning bar. Since it is not necessary to accommodate a bearing race between the bearing elements and the turning bar, a turning bar of greater diameter can be used, and this improves the rigidity and accuracy of the surfacing machine. Each support chuck includes radially extendible legs for contacting the workpiece wherein each leg is individually adjustable and a separate distance gauge is used to measure its radial position to aid in aligning the surfacing machine relative to the workpiece. The drive mechanism is mountable along the length of the turning bar and includes a rotational drive motor coupled to the turning bar. The drive mechanism is held against all but axial movement relative to the support chucks such that operation of the motor causes the turning bar to rotate relative to the chucks. Axial positioning of the tool support arm is permitted by movement of the drive mechanism relative to the support chucks.

Brief Description of the Drawings For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings in which: FIG. 1 is a side view of a first surfacing machine embodying the present invention;

FIG. 2 is a bottom view of the machine of FIG. 1 better illustrating a tool support arm thereof;

FIG. 3 is a sectional view of a portion of the machine of FIG. 1 depicting a bearing arrangement for rotationally supporting a turning bar while allowing axial movement thereof;

FIG. 4 is a top view of the machine of FIG. 1 showing portions of the rotational drive and axial positioning mechanisms; FIG. 5 is a side view partially cut away of a surfacing machine in accordance with the invention mounted within a valve body;

FIG. 6 is a top view partially cut away of a support chuck of the machine of FIG. 5; FIG. 7 shows a bearing arrangement of the support chuck of FIG. 6 which provides rotatable support while allowing axial movement of a turning bar;

FIG. 8 is a partial cut away view of the support chuck of FIG. 6;

FIGS. 9 and 10 are sectional views illustrating a tool support arm and tool head assembly utilized in the machine of FIG. 5;

FIGS. 11, 12 and 13 illustrate a rotational and axial drive mechanism of the machine of FIG. 5;

FIG. 14 is a sectional view of the turning bar which illustrates a rotary union and the placement of a hose and a control rod within the turning bar; FIGS. 15 and 16 are sectional views of the tool support arm with a grinding tool head assembly attached thereto;

FIG. 17 depicts use of additional components used in connection with the machine of FIG. 5; and FIGS. 18 and 19 illustrate extension tools used in connection with the surfacing machine.

Detailed Description FIG. 1 shows a first surfacing machine in accordance with the present invention mounted within a cylindrical bore 10 defined by a workpiece 12 for surfacing portions of the workpiece 12. A keyless turning bar 14, having a hardened external surface 16 of circular cross-section defining a central axis 18, is rotatably and concentrically supported within ^' the bore 10 by an upper support chuck 20 and a lower support chuck 22, each support chuck having a chuck body 24 and radially extensible legs 26 for engagement with the workpiece 12. The legs 26 are threaded within the corresponding chuck body 24 and the support chucks 20 and 22 are mounted within the bore 10 by rotation of the legs 26 to bring each of the legs 26 against the workpiece 12 while concentrically positioning the central axis 18 of the turning bar 14 within the bore 10. Each of the support chucks 20 and 22 includes a bearing arrangement 28 (FIG. 3) which rotatably supports the turning bar 14 while allowing axial movement of the turning bar 14. " More particularly, each bearing arrangement 28 comprises an outer bearing race 30 affixed to the corresponding chuck body 24 and needle roller bearings 32 captive be¬ tween the outer bearing race 30 and the external surface 16 of the turning bar 14. To provide the turning bar 14 with maximum alignment stability within the support chucks 20 and 22, the needle bearings 32 are in a preloaded condition between the race 30 and the turning bar 14. The needle bearings 32 are each rotatable about an axis of rotation 34 parallel to the central axis 18. The turning bar 14 is thus permitted to both rotate

about and translate along its central axis 18, relative to the support chucks 20, 22. In this manner, the external surface 16 of the turning bar 14 forms an inner race for the bearings 32 and permits the support chucks 20 and 22 to be con¬ veniently positionable along the length of the turning bar 14.

A tool support arm 40 (FIGS. 1 and 2) is mounted on the turning bar 14 for carrying a sur- facing tool 42 radially spaced from the central axis 18 such that rotation of the turning bar 14 causes the tool 42 to rotate about the central axis 18. At a proximal end 44 of the support arm 40, a mounting block 46 having an aperture 48 adjustable in diameter receives the turning bar 14 while bolts 50 close the aperture 48 upon the turning bar 14 to tightly ^' secure the tool support arm 40 on the turning bar 14. At a distal end 52 of the support arm 40, a removable tool head 54 carries the surfacing tool 42 for engagement with the workpiece. The arm 40 is adapted to receive various tool heads for different surfacing operations, such as grinding or the like. For tool heads requiring a source of power, such as electrically or pneumatically transmitted power, the turning bar 14 may be tubular, and wires and hoses may be disposed within the turning bar 14 for coupling a tool head to a source of power. Thus, the support arm 40 is mountable along the length of the turning bar 14. As shown, the arm 40 is positioned below the chucks 20 and 22; however, it is understood that the bearing arrangement 28 and the keyless turning bar 14 make many configurations possible such as placing the arm 40 above or between the chucks 20 and 22, as required by the

contour of a given workpiece or the nature of a given surfacing operation. Further, removal of the arm 40 would allow removal of the bar 14 without dismounting the chucks 20 and 22 such that a given mounting alignment may be preserved if it were necessary to reconfigure the machine during a surfacing operation.

A drive mechanism 60 (FIGS. 1 and 4) is posi¬ tioned at an upper end 62 of the turning bar 14 and used to impart rotational and axial movement to the turning bar 14. The drive mechanism includes a housing 64 which is rotatably mounted on the turning bar 14 and carries a rotational drive motor 66 and an axial drive motor 68. The housing 64 is ^• held against rotation about the central axis 18 relative to the support chucks 20 and 22 by a guide member 70 secured to the upper support chuck 20 by a tubular support 72 affixed to the chuck 20 and coaxial to the surface 16. The guide member 70 is held between pegs 74 affixed to the housing 64, the pegs 74 permitting axial movement of the guide member 70 therebetween. The rotational drive motor 66 is coupled to the turning bar 14 by a drive chain 76 such that operation of the rotational drive motor 66 serves to rotate the turning bar 14 relative to the support chucks 20 and 22. An axial lead screw 80 is rotatably secured to the housing 64 by a thrust bearing (not shown) and threadably engaged with the body 24 of the upper support chuck 20. The axial drive motor 68 is coupled to the axial lead screw 80 by gears 82 such that operation of the axial drive motor 68 in a first direction brings the housing 64 toward the upper support chuck 20 while operation in a second direction moves the housing 64 away from the upper support

chuck 20 to effect up and down motion of the tool 42 relative to the workpiece 12.

By providing the turning bar 14 with rotational and axial movement relative to the support chucks 20 and 22 and by placing the drive mechanism 60 at the upper end 62 of the turning bar 14, it is possible for an operator to see clearly the work site and, more importantly, provides the operator with access to the work site to allow exchange of the tool head 52 for switching, for example, from a cutting operation to a grinding operation. There is no need to dismount the surfacing machine to exchange tool heads, and as a result less material is removed from the workpiece 12 and less time is required to surface the workpiece 12. Further, by eliminating the inner race for the bearing arrangement 28 ^* , a turning bar of larger diameter may be used which contributes greatly to the rigidity of the surfacing machine and the accuracy of its operation. Finally, because the support chucks 20 and 22 and the tool support arm 40 are positionable along the length of the turning bar 14, the surfacing machine is adaptable to many types of workpieces without a need for special mounting surfaces.

FIG. 5 shows a second surfacing machine in accordance with the invention mounted within a valve body 110 for surfacing a valve seat 112. A turning bar 120, having an external surface 122 of circular cross-section defining a central axis 124, is rotatably supported within the valve body 110 by an upper support chuck 126 and a lower support chuck 128, each support chuck engaging the valve body 110 for mounting the surfacing machine therein. A tool support arm 132 is mounted at one

end of the turning bar 120 and carries a removable tool head assembly 134 while a rotational and axial drive mechanism 136 is positioned at an opposite end of the turning bar 120 for providing the bar 120 with rotational and axial movement about and along the axis 124 relative to the support chucks 126 and 128.

FIGS. 6-8 further illustrate the lower support chuck 128 wherein a leg 130a is radially slidable with respect to the axis 124 within a cavity 140a (FIGS. 6 and 7) formed in the support chuck 128, the leg 130a and cavity 140a each having a square cross section for preventing rotation of leg 130a within the cavity 140a. Radial positioning of leg 130a is accomplished by rotation of screw 142a threadably engaged within leg 130a and held against radial movement relative to the axis 124 by thrust washers 144a. As shown in FIG. 8, the screw 142a includes a worm gear 146a meshed with a worm 148a rotationally disposed within chuck 128, the worm

148a having a nut 150a for rotation thereof. Thus, rotation of nut 150a in one direction causes leg 130a to be advanced radially outward with respect to axis 124 while rotation of nut 150a in the opposite direction results in radial retraction of the leg 130a relative to the axis 124.

A distance gauge 154a (FIG. 7) indicates the radial extension of leg 130a with respect to the axis 124 by means of pin 156a affixed to leg 130a and contacting a sensing rod 158a of gauge 154a, the rod 158a being spring biased radially outward with respect to the axis 124. As leg 130a is moved radially, the sensing rod 158a follows the pin 156a such that the gauge 154a provides a measure of the radial position of the leg 130a, Gauge 154a may be

reset to zero when leg 130a is at an arbitrary radial position, for example when it engages a reference surface at a predetermined radial distance from the external surface 122 of the turning bar 120.

The lower support chuck 128 further includes radially extendible legs 130b and 130c and corre¬ sponding gauges 154b and 154c individually operated by rotation of nuts 150b and 150c, respectively, in similar fashion to that of leg 130a and gauge 154a. Also, the upper support chuck 126 includes three radially extendible legs and corresponding gauges each similar to leg 130a and gauge 154a and individually operable by rotation of separate nuts. The support chuck 128 includes a bearing arrangement 160 (FIG. 7) which rotatably supports the turning bar 120 while allowing axial.movement of .the turning bar 120. More particularly, the bearing arrangement 160 comprises an outer bearing race 162 affixed to the chuck 128 and needle roller bearings 164 captive between the outer bearing race 162 and the external surface 122 of the turning bar 120. The needle bearings 164 are rotatable about axes of rotation parallel to the central axis 124. The surface 122 is suitably hardened and forms an inner race for the bearings 164. To provide the turning bar 120 with maximum alignment stability within the support chuck 128, the needle bearings 164 are in a preloaded condition between the race 162 and the turning bar 120. The turning bar 120 is thus permitted to both rotate about and translate along its central axis 124 relative to the support chuck 128, which is thereby conveniently positionable along the length of the turning bar 120.

The turning bar 120 may be temporarily locked in position relative to the chuck 128 by split lock bars 170 (FIG. 6) affixed to the chuck 128, each of the lock bars 170 having a surface 172 adjacent and generally parallel to the surface 122 of the turning bar 120. Lugs 174, each threadable within a corresponding one of the lock bars 170, are employed to urge the corresponding surface 172 against the surface 122 of the turning bar 120 with sufficient force to prevent rotational and axial movement of the turning bar 120 with respect to the chuck 128.

The chuck 126 has a bearing arrangement similar to the bearing arrangement 160 of chuck 128 and a set of lock bars similar to the lock bars 170 of the chuck 128.

The tool support arm 132 is coupled to the bar 120 ^' by a split-clamp mounting block 180 (FIG. 9) having an aperture 182 adjustable in diameter for receiving the turning bar 120 while bolts 184 close the aperture 182 upon the turning bar 120 to tightly secure the tool support arm 132 on the turning bar 120. The tool support arm 132 is formed with a dovetail 186 slidable in a mortise 185 of the mounting block 180. Set screws 188 secure the tool support arm against sliding movement relative to the mounting block during machine operation and are releasable to provide gross adjustments in the radial positioning of the tool head assembly 134 with respect to the central axis 124.

The tool head assembly 134 carries a cutting tool 190 on a rack 192 (FIGS. 9 and 10) driven radially with respect to the central axis 124 by a pinion 194 rotatably disposed within the tool head

assembly 134. Pinion 194 is coupled to worm gear 196 meshed with a worm 198 rotatably mounted in the tool head assembly 134 such that rotation of the worm 198 effects radial positioning of the rack 192. A block 200 mounted interiorly of the tubular turning bar 220 by bolts 201 suppor-ts a worm 202 rotatable by means of a radial feed rod 204 rotatably disposed longitudinally within the turning bar 120. The worm 202 is employed to rotate a worm gear 206 within the block 200. A hexagonal rod 208, slidable along and rotatable about an axis 209, is slidable within a hexagonal aperture of the worm gear 206 and slidably engageable with the worm 198 at a dis-engageable connection 210. When the rod 208 is inserted in the connection 210, rotation of the radial feed rod 204 is transmitted via worm 202, worm gear 206, rod 208, worm 198, worm gear 196 and pinion 194 for radial positioning of the tool 190. Removal of the rod 1108 from the connection 210 disengages radial feeding of the tool 190.

A radial engagement mechanism 212 is mounted on the block 180 and is used to slide the rod 208 in and out of the connection 210 for coupling and decoupling the tool head assembly 134 from radial feeding. To this end, a rotatable shaft 214 includes an eccentric pin 216 radially spaced from a rotational axis 218 of the shaft 214. A clutch block 220 is affixed to the rod 208 and includes a channel 222, transverse to a plane containing rod

208, for receiving the eccentric pin 216. Rotation of the shaft 214 causes the eccentric pin 216 to urge the block 220 toward and away from the tool head assembly 134 and thereby engages and

disengages the rod 208 at the connection 210. The shaft 214 is rotated by a nut 224.

The tool head assembly 134 includes a tool head 242 formed with a mortise 231 which receives a dovetail 230 of the tool support arm 132, the dovetail 230 and mortise 231 converging in an upward direction. A clamping plate 238 is attached by bolts 239 to the tool head 242 at its upper end. Thus, the tool head assembly 134 may be brought to rest on the tool support arm 132 and supported thereon by engagement of the mortise 231 with dovetail 230 and engagement of the plate 238 with the arm 132. A tool head lock screw 236, having a nut 237 and threadable within the tool support arm 132, secures the tool head assembly 134 on the tool support arm 132. The lock screw 236 is captive upon the"clamping plate 238 between upper and lower thrust discs, but is rotatably disposed upon plate 238 such that rotation of lock screw 236 in the clockwise direction serves to press the tool head 134 onto the mortise 231, and rotation in the counterclockwise direction serves to lift the tool head 134 from the mortise 231.

A swivel tool head 240 (FIG. 9) of the. tool head assembly 134, including the rack 192, is rotatable with respect to the tool head 242, including the worm 198 and dovetail 230, about an axis 244. A swivel lock nut 246 and swivel clamp 248 serve to lock the swivel tool head 240 with re- spect to the tool head 242 during operation of the surfacing machine and permit selective rotational positioning of the tool 190 about the axis 244 for changing the angle of cut with respect to the axis 124. This arrangement allows for swiveling of the

tool 190 while maintaining connection 210 in posi¬ tion to receive the rod 208.

Drive mechanism 136 (FIGS. 11, 12 and 13) imparts both rotational and axial movement to the turning bar 120 about and along its central axis

124. The drive mechanism 136 includes a block 250 with a split ring collet 252 rotationally disposed therein upon roller bearings 254 and thrust bearings 255 (FIG. 13). A screw 256 and split ring clamp 258 are used to tighten the collet 252 about the turning bar 120. Thus, the bar 120 is rotatable with respect to the block 250 and the position of the drive mechanism 136 along the length of the bar 120 may be adjusted. Needle bearings 260 are mounted on the block 250 and contact the surface 122 to provide additional rota¬ tional support between the turning bar 120 ^" and the block 250. .The collet 252 is fitted with worm gear 262 meshed with worm 264 affixed to a rotational drive shaft 266 driven by a rotational drive motor 268. Operation of the rotational drive motor 268 causes the turning bar 120 to rotate about its central axis 124 relative to the block 250. A bi¬ directional axial drive motor 272 turns an axial drive shaft 274 having worms 276 axially spaced therealong for engagement with corresponding worm gears 280. Each of worm gears 280 is connected to a corresponding axial lead screw 284. Axial lead screws 284 are rotationally disposed in block 250 and extend toward the upper support chuck 126. Thus, the axial lead screws 284 are driven bi- directionally by the axial drive motor 272.

A tubular member 290 (FIG. 5) concentric to the turning bar 120 and affixed to the upper support chuck 126 extends from the upper support

chuck toward the drive mechanism 136. The member 290 is provided with apertures (not shown) for permitting the lock bars 170 to be positioned ad¬ jacent the turning arm 120. Axial lead screws 284 are threadably engaged in an upper portion 292 of the support member 290 such that rotation of the axial lead screws 284 in one direction causes the turning bar 120 to move axially in one direction relative to the upper support chuck 126 while rotation of the axial lead screws 284 in the opposite direction moves the turning bar 120 in the opposite axial direction.

The drive mechanism 136 is held against rota¬ tion about the central axis 124 relative to the support chuck 126 by guide members 300 (FIGS. 5,

11, 12 and 13) secured to the tubular support 290. The guide members 300 are held between pegs 302, affixed to the block 250, which permit axial movement of the guide members 300 therebetween. A cap 310 (FIG. 14) at an upper end 312 of the turning bar 120 is provided with a bearing 313 for rotational support of the radial feed rod 204. A radial feed nut 314 is provided at the upper end of the rod 204 for r tation thereof to perform radial positioning of the tool 190 relative to the central axis 124. The gearing ratios among the various gears coupling the nut 314 to the rack 192 may provide, for example, 0.127 mm radial movement of the rack 192 per revolution of the nut 314 relative to the turning bar 120. A fixed radial feed rate during machine operation is achieved by holding the radial feed nut 314 against rotation about its central axis with respect to the support chuck 126, while the turning bar 120 is rotated at a constant

rate under the influence of the rotational drive motor 268.

A separate grinding tool head assembly 350 (FIGS. 15 and 16), comprising a tool head 392 and a slidable tool head 396, is mountable on the tool support arm 132 by means of a mortise 352 formed in the tool head 392. Mortise 352 is similar to mortise 231 of the tool head assembly 134. Grinding tool head assembly 350 also includes a clamping plate 367 and lock screw 369, similar to plate 238 and lock screw 236, respectively, of tool head assembly 134. The grinding tool head assembly 350 includes a pneumatic motor 354, for rotating a grinding wheel 355. The motor has an intake air hose 356 and an exhaust air hose 358, the air hoses 356 and 358 each having a nipple 359 at its distal end relative to the motor 354. Nipples 359 are ^• secured within clamping plate 367. Hoses 360 and 362 are routed through a cavity 364 in .the tool support arm 132 and terminate at fittings 366 and

368, respectively, in the tool support arm 132 near the dovetail 230. As the grinding tool head assembly 350 is lowered onto the dovetail 230 of the tool support arm 132, nipples 359 of the hoses 356 and 358 are received in fittings 366 and 368, respectively, to establish a pneumatic coupling between the motor 354 and the hoses 360 and 362. The lock screw 369 and plate 367 secure the grinding tool head assembly 350 to the tool support arm 132 and the nipples 359 within the fittings 366 and 368.

The hoses 360 and 362 are affixed to the turning bar 120 at an area 370 (FIG. 14) immediately above the tool support arm 132. The hose 360, carrying the intake air for the motor

354, is coupled through the wall of the turning bar 120 to a hose 372 longitudinally disposed within the bar 120, the hose 372 being coupled at an opposite end to the cap 310. The cap 310 includes an annular groove 374 coupled to the hose 372 by an airway 376 and is adapted to rotatably receive a sleeve 378 having a radial airway 379 which is coupled to an air source hose 380. The sleeve 376 and cap 310 form a rotary union for providing compressed air from the air source hose 380 through the airway 379 and into the groove 374 and airway 376 such that the compressed air is then communicated via the hoses 372, 360, and 356 to the motor 354. The exhaust from the motor 354, carried in the hose 362, is vented into the turning bar 120 at the connection of the hose 362 to the bar 120. The cap 310 is suitably provided with vents 384 to allow the air exhaust to escape from the turning bar 120. It is desirable to seal the turning bar 120 at its lower end with a cap 410, and also at rotational support points 386 for the rod 208, to insure that the motor exhaust exits the turning bar 120 only at the upper end. By venting the motor exhaust through the upper end of the turning bar 120, away from the work site, debris produced during the surfacing operation is not widely spread throughout the valve body 110.

The grinding tool head assembly 350 includes an engageable connection 390, similar to the connection 210 of the tool head assembly 134, which receives the rod 208 for radial positioning of the grinding wheel 356. Tool head 392 further includes a mortise 394 upon which the slidable tool head 396, including the motor 354, is radially slidable with respect to the axis 124 upon a dovetail 398.

A carriage screw 400 is coupled to the connection 390, rotatably disposed with respect to the tool head 392, and threadably engaged with the slidable tool head 396 such that rotation of the carriage screw 400 by the rod 208 effects radial movement of the motor 354 and grinding wheel 355 with respect to the central axis 124.

The surfacing machine is provided with ad¬ ditional components for purposes of versatile ope- ration. Cap 410 (FIG. 10), threaded within a lower end of the turning bar 120, is removed to allow attachment of an extension bar 412 (FIG. 17) which is threadable within the lower end of the turning bar 120. The extension bar 412 is identical in cross section to turning bar 120 and is rotatably supported by the chuck 128. The extension bar 412 facilitates mounting of the lower support chuck 128 below the tool support arm 132 such that the tool support arm 13-2 is intermediate the support chucks 126 and 128. Additionally, a tubular standoff 414 is bolted externally of the valve body 110 to permit the upper support chuck 126 to be mounted therein and positioned outside the valve body 110 for operation of the tool head assembly 134 close to an upper edge 416 of the valve body 110.

The tool head assemblies 134 and 350 are easily mounted and dismounted on the tool support arm 132 even when they are deep within the valve body 110 and out of the operator's reach. Exten- sion socket tool 420 (FIG. 18) is of sufficient length to reach deep within the valve body 110 and has a socket 421 adapted to perform several tasks such as rotate the lock screws 236 and 369 to mount and dismount the tool head assemblies 134 and 350, turn the nuts 150 to radially position the legs 130

of chucks 126 and 128, turn the nut 224 to engage and disengage the rod 208 within the connections 210 and 390 to permit mounting and dismounting of the tool head assemblies 134 and 350, and adjust the lugs 174 to lock and unlock the chucks 126 and 128 on the turning bar 120. Extension screw tool

422 (FIG. 19) is also capable of reaching deep within the valve body 110 and has a threaded end

423 for threaded engagement with threaded apertures in the tool head assemblies 134 and 350, e.g., aperture 424 shown in FIG. 15, in order to lower or raise the tool head assemblies 134 and 350 to and from the tool support arm 132 while the machine is mounted within the valve body 110. The hoses 360 and 362 shown in FIGS. 14, 15, and 16 have not been shown in FIGS. 9 and 10 for purposes of clarity; however, it is understood that these hoses remain attached to the surfacing machine. The clamping plate 238 (FIGS. 9 and 10) is provided with plugs (not shown) for insertion into the fittings 366 and 368 (FIGS. 15 and 16) for sealing the fittings 366 and 368 during cutting operations.

To install and operate the surfacing machine, the support chucks 126 and 128 are locked to the turning bar 120 by tightening the lugs 174. The chucks 126 and 128 should be positioned such that the machine is stable and generally aligned for insertion in the valve body 110 when hoisted at a lifting point on the tubular support 290. The gauges 154 are all reset when the legs are extended to a common predetermined distance from axis 124. The machine is then placed in the valve body 110 and the legs 130 are extended to contact the valve body and secure the support chucks 126 and 128

therein, the gauges 154 being used to position the central axis 124 of the turning bar 120 relative to the valve body 110. The lugs 174 are loosened to allow rotational and axial movement of the turning bar about and along the central axis 124. The tool head assembly 134 may be axially positioned, by operation of the motor 272, adjacent to the area to be surfaced. Activation of the motor 268 causes the tool head to rotate about the axis 124. By holding the radial feed nut 314 against rotation while the turning bar rotates, the tool 190 is fed radially outward at a constant feed rate. In this manner, a cutting operation is performed.

Once the cutting operation is complete, the tool head assembly 134 is removed from the tool support arm 132. An operator uses the extension tool 420 to first access the nut 224 to slide the rod 208 out of the connection 210 and then to rotate the lock screw 236 to release the tool head assembly 134 from the tool support arm 132 whereupon the tool 422 is used to lift the tool head assembly 134 from the tool support arm and remove it from the valve body 110. The grinding tool head assembly 350 is then lowered onto the tool support arm 132 using the tool 422 and the nipples 359 are received in the fittings 366 and 368. The extension tool 420 is then used to rotate the lock screw 369, to secure the grinding tool head assembly 350 on the tool support arm 132, and to rotate the nut 224, to engage the rod 208 in the connection 390 to permit radial feeding of the grinding tool head assembly 350.

By providing the turning bar with rotational and axial movement relative to the support chucks and by placing the drive mechanism externally of

the valve body 110, it is possible for an operator to see clearly the work site and, more importantly, provides the operator with access to the work site. There is no need to dismount the surfacing machine to exchange tool head assemblies, and as a result less material is removed from the valve body and less time is required to surface the valve body. Further, by eliminating the inner race for the bearing arrangement, a turning bar of larger diame- ter may be used which contributes greatly to the rigidity of the surfacing machine and the accuracy of its operation. Finally, because the support chucks and the drive mechanism are adjustable in position along the length of the turning bar, the surfacing machine is adaptable to many types of valve bodies without a need for special mounting surfaces, and adaptable to many types of surfacing operations including refinishing pressure seal bores and surfacing guide ribs of large steam isolation valves.

It will be appreciated that the present inven¬ tion is not restricted to the particular embodiment that has been described and illustrated, and that variations may be made therein without departing from the scope of the invention as defined in the appended claims and equivalents thereof.