Patent GB-530101-A (GB)
Title: Improvements in or relating to milling machine tools
IPC: B23C3/24
Filed: 1939-10-18
Abstract: 530,101. Milling-machines; cutters. NATIONAL BROACH & MACHINE CO. Oct. 18, 1939, No. 28096. Convention date, Nov. 21, 1938. [Class 83 (iii)] In a method of and machine for milling workpieces of circular section the workpiece is quickly traversed laterally up to a pair of continuously rotating milling cutters,then fed slowly to depth, then slowly rotated to spread the cut round the work and then quickly withdrawn from the cutters. The machine has a primary base 1 with end columns 2, 3 supporting an upper base 4 this structure being further stiffened by a strut 49h. Two cutter spindles 9, 10 depend from the upper base and are driven from motors 8 through speed change mechanism 7. A rigid work-holding slide 101 is guided on both bases 1, 4 being provided with a roller 80 which rolls on a wear plate on the base 1, Fig. 6, and with end supports 89, 90 connected by a bar 91 sliding on a wear plate on the upper base. The two vertical work-supports each comprise a vertically-movable headstock 100 and corresponding tailstocks 92a. A container 76 receives coolant and chips from apertures 1c in a frame wall 1b, the coolant being circulated by a pump 74 driven by a motor 73. The slide 101 is traversed by a motor 13 which drives a feed screw 16. Each of the cutter driving motors 8 is mounted on a base 8a adjustably clamped to the base 4. The motor is connected by V belts to a shaft 27 which is further connected by bevel gears 36, shaft 37, spur gears 41 shaft 43 and spur gears 46 to the cutter spindle 48, the latter being mounted in a separate housing 36. A splined part 49 is adapted to receive the cutters 9 or 10. In the form shown the movement of the slide 101 carries the workpiece between the opposed cutters and the work may be completed by a rotary movement of substantially 180 degrees if the cutters are identical or 360 degrees if the cutters are different. The cutter housings 36 are pivotally movable about shafts 43 to adjust the cutter spindles for work of different diameters, this adjustment being effected by worm gears 36f. The housings are secured after adjustment by a bar connecting the housings together and by bolts 60 which secure the housings to the base 4. The lower end of the rear cutter spindle is steadied by supports 49e bolted to the frame part 1b and the lower end of the front cutterspindle is supported by a bracket 49d secured to a strut 49h connecting the bases 1 and 4. Each headstock is supported in an upper bearing 103 and also in lower bearings 108 within a sleeve 111 which is moved vertically to adjust the headstock by rack-and-pinion mechanism 120 actuated from a lever 114. Drive of the headstock is effected from a two speed motor 122 through a coupling 128, worm gearing 137, and a shaft 139 which is connected by change gearing, worm gearing 159 and spur gearing 164 to the work spindle. In one arrangement, Fig. 35, an adaptor 100a is keyed at 100c to the work spindle and carries pins 100b engaging holes in the lower flange of a work piece W. A centering pin 100g engages the bore of the workpiece. The bar 91 is provided with a back centre pin 92a engaging the upper part of the work. In a modification, Fig. 32, the headstocks may be raised and lowered by power means. For this purpose a fluid pressure cylinder 450. has a rod connected to a rack 454 engaging a pinion 456 geared to the headstock spindle. A reversing valve controlling the cylinder may be actuated by trip mechanism to raise the headstock as the spindle moves towards the cutters and to lower it as it comes to rest in the loading position. The workslide 101 moves along ways 20 and is fed by a screw 16 driven from motor 13 at either feed or traverse speeds. The motor housing is secured to the column 3 and its shaft 200 carries a traverse gear 205 and a feed gear 209 these two gears being connected respectively with gears 235 and 230 loose on a shaft 240 by independent driving trains. The gears 230, 235, are selectively clutched to the shaft 240 by a splined clutch member 252. Bevel gearing 254 connects the shaft 240 to the feed screw 16 which is mounted in ball bearings and runs in a nut member having relatively adjustable parts 274a, 274b. The speed-changing clutch 252 is actuated by a shifter rod 379 which may be actuated by a solenoid 352, Fig. 30. When the solenoid is energized a plunger 353a is actuated to shift the rod 379 and to tension a spring 372 which returns the parts when the solenoid circuit is broken. In a modification the solenoid may actuate a cam plate to operate the clutch shifter. The work spindle motor is started only when the work has been brought to a position adjacent the opposed cutters. The shaft 160 of the work-driving train carries a projection 425a, Fig. 6, connected by gears 427, to a shaft 428 which rotates at approximately the same speed as the work. The shaft 428 carries a cam operating a switch C1. The table 101 carries adjustable trip dogs 319a, 320a, Fig. 6, which operate switches G, G1, Fig. 10, in the control of the clutch 252. The cutter spindle motors 8 and the coolant motor 73 are continuously driven during operation of the machine and are controlled by the switches 303, 304. The workdriving motors 122, 122<SP>1</SP> are provided with interlocked switches 312, 314, which cause alternate actuation of the two spindles, one spindle being worked while the other is loaded. The table 101 has a reversing motor 13 controlled by a switch 316 which is interlocked with switches 312, 314 to determine the operation of the work motors in accordance with the direction of slide movement. In one method of operation a movement is started by switches Y or Y<SP>1</SP> and the table stops at the end of each translation. By moving selector switch Z an entirely automatic operation controlled by trip switches C, C<SP>1</SP>. D, D', G and G<SP>1</SP> is obtained. The solenoid 318a operates the rate selector 252, the change being effected by the dogs 319a and 320a. When on movement of table 101 to the right dog 319a engages switch G, solenoid 318a causes a speed change to feed position, the table being finally stopped by switch D<SP>1</SP>. This is followed by starting of motor 122<SP>1</SP> to machine the piece carried by the headstock 100 to size. A trip 326 then actuates switch C<SP>1</SP> to stop motor 122<SP>1</SP>, reversely start the slide motor 13, and shift solenoid 318a to rapid traverse position, the cutting cycle being then repeated at the other headstock. In some cases two or more cuts may be taken. In this case the control circuit is modified so that the slide 101 is first stopped at the end of a first feed movement whereat the work is rotated while a coarse cut is taken and is then fed further towards the cutters to a second position where the work is again rotated while a second cut is taken. The speeds of the motors 8 or 122, 122<SP>1</SP> or both may be adjusted so that the finishing cut is taken at a higher speed. A number of different work cycles are described. Thus in Fig. 20 the work may be traversed from A to B, fed slowly to the maximum cut position C between the cutters 9, 10, then rotated through rather more than 180 degrees to finish the work and then quickly withdrawn. A similar cycle may be performed where two workpieces are moved alternately to a position between the cutters. In some cases only a single cutter is employed, the work being then rotated through 360 degrees. In Fig. 22 a two-stage feed is employed the work being traversed from A to B then slowly fed to B<SP>1</SP> where it is rotated for a first cut, then stopped and fed to C where it is rotated for a finishing cut before it is finally withdrawn. A similar cycle may be used with a single cutter. In another modification two headstocks are arranged, Fig. 24, on off-centre positions on the workslide. The work is first fed on the spindle A to the cutter 9 for a rough cut and is then withdrawn transferred to spindle A<SP>1</SP> whereon it is fed to cutter 10 for a finishing cut. Or the two cuts may be taken by moving a single work spindle in the same direction first to one cutter for a roughening cut and then to a second cutter for a finishing cut. In other modifications the work may be continuously rotated as it is fed between the cutters. In a further modification, Fig. 29, a circular work-table is employed and the pieces are fed successively to roughing cutters 9, 10 and finishing cutters 9<SP>1</SP>, 10<SP>1</SP>; or further sets of cutters may be employed. The cutters may have a pitch of about <SP>5</SP>/ 16 inch to #inch and may take a cut of .005 inch per foot at a cutting speed of 100 feet per minute or more. A typical set-up of the cutters is shown in Fig. 42. One of the opposed cutters has cutting sections C 1 , C 3  and C 5  and the other cutting sections C 2  and C 4 , these sections forming the corresponding sections S 1  ... S  5  on the work.