Patent GB-650673-A (GB)
Title: Improvements in and relating to metal cutting and like machine tools
IPC: B23G5/10
Filed: 1946-05-24
Abstract: 650,673. Screwing die-heads ; taps. LANDIS MACHINE CO. May 24, 1946, No. 15789. Convention date, June 4, 1945. [Class 83 (iii)]  In a machine for cutting parallel or tapered screw threads, an interchangeable cutter head 34, Fig. 1, for producing either internal or external threads is carried by a rotary spindle on an axially fed slide 32, and a housing 214 on the slide contains mechanism for adjusting the diameter of cut and degree of taper for either cutter head through operating means which extend co-axially and rearwardly from the head. Alternatively, the work may be fed axially relatively to the cutter head or the work may be both rotated and fed axially. . Screwing die-heads.-For external screwing the head 34 comprises rear and front portions 41, 44, Fig. 3, whereof the latter has approximately radial guides 70 for slides 72 having tangential chasers 78 secured thereto by clamps 82, the cutting edges of the chasers being radially adjustable by bevelled keyways 118 in axially moving plungers 108. The keyways engage keys on pads 122, Figs. 3 and 6, freely rotatable in circular dovetailed recesses 124 in the slides 72. The plungers 108 are individually adjustable on a spider 100 by means of screwed stems 106 and gear-nuts 110, 112 which engage pinions 126, 134, Fig. 6, carried by hollow and solid concentric shafts 128, 132 respectively projecting to the front of the head. To adjust a chaser individually the gears are rotated by keys engaging the shafts at 130, 136 to loosen the nuts on the stem 106, after which one shaft is rotated to move the stem axially by the required amount, and the nuts are then re-locked against a spacing sleeve 114. A graduated scale and pointer on each of the sockets 130, 136 facilitates adjustment. The spider 100, which is guided between ribs 101 on the rear portion 41 of the head, is moved axially for opening and closing all the chasers simultaneously by means of a non-rotatable rod 196 journalled therein by ball bearings 194. The bearings are located in sleeves 186, 192 secured to the spider and are fixed axially on the rod by locked nuts 200, 206, oil seals 204, 208 being provided. A conical member 212 may be secured by screws to the part 44 of the head for centring hollow work. The head is secured to the driving spindle 56 by a flange nut 62 and the torque is transmitted by a radial key 58. Taps.-For internal screwing an expanding tap replaces the head 34 and comprises rear and front portions 442, 444, Fig. 22, the latter carrying radially slidable chasers 448 having bevelled grooves 450 engaging similar ribs 452 on a conical head 454 which is attached by a screwed pin 472 to a tubular member 466. This member is secured by screws to the sleeve 192 rotatable on the draw rod 196 in the same manner as for the. die-head, and is keyed at 485 to the body part 442 so as to receive axial motion from the draw rod for moving the chasers radially through the head 454. The forward end of the body is closed by a plate 492 which is a friction fit in the aperture. The chasers are set by rotating the pin 472 through a wrench inserted in its forward end, the set position being secured by balls 484, Fig. 25, in the head 474 of the pin, pressed by a spring 480 into contact with serrations 486 in the recess 475 of member 466 in which the head rests. Opening and closing die-heads and taps ; set position indicating and determining. - The mechanism for giving axial movement to the draw rod 196 relatively to the cutter head, and enclosed within the housing 214, consists of a cylinder 228, Fig. 9, secured to the rod and slidable within a shell 224 slidable in the housing. A piston 244 within the cylinder is fixed axially in the member 224 by nuts 288, 290 screwing on its rod 248. The nut 288 has gear teeth so that it may be rotated by a handoperated pinion on a parallel shaft to allow the pinion 290 to be rotated by a wrench applied at 292 in order to adjust the axial position and therefore the diameter of cut, the nut 288 then being rotated for re-locking. A sleeve 296, Figs. 9 and 19, is splined in a tubular extension 300 attached to the shell 224 and has an internal square thread engaging a similar thread 297 on a bush 298 splined on the nut 290 which is held axially stationary by its flange 290<SP>1</SP>. An aperture 302 in the extension 300 and a helical slot 304 in the sleeve 296 enable a graduated scale 306 on the thread 297 to be observed against an index 308 on the slot 304 so that the axial rotation given to the nut 290 and hence the diameter of cut may be read. An index 316 on the aperture 302 reads against an index 318 on the slot 304 at zero position of the scale to indicate the direction of adjustment. Compressed air or hydraulic fluid is admitted through either of the nipples 260, 276, to one end or the other of the cylinder 228 and moves the cylinder and rod 196 to effect opening and closing of the cutter head. A key 232 prevents rotation of the cylinder 228 relatively to the shell 224 and a further key prevents rotation of the piston rod 248 in the shell. Fluid from nipple 260 passes through the hollow piston rod and through passages 264 under a coverplate 266 held to the piston by studs 268, these studs passing into recesses 438 in the end of cylinder 228 when a die-head is in use to allow a full stroke. When using a tap, however, the piston 244 and end covers 236, 242 of the shell 224 are secured to the shell in a different angular position so that the studs will engage the end of the cylinder to limit the stroke of rod 196, this position being indicated by keys 435, Fig. 20, and an index 433. Taper threading mechanism.-To cut a tapered thread, with the cylinder 228 holding the draw rod 196 in cutting position, the slide 32 is fed at the speed corresponding to the pitch of the thread being cut and the shell 224 is moved at a different speed so as to move the piston, cylinder and rod 196 relatively to the cutter head. To effect this a pivot 332, Figs. 9 and 10, in the shell 224 has a slot 335 in which a bar 328 is slidable. The bar 328 also slides through a trunnion 326 journalled in a bracket 322 secured to a pedestal 320 fixed on the machine frame so as to constitute a fixed pivot, whilst a trunnion 330 is attached to the bar and is journalled in a block 336 normally stationary on the shell 224 but vertically adjustable thereon. If the axes of pivot 332 and trunnion 330 are the same distance from trunnion 326, a parallel thread will be cut, and if the block 336 is adjusted upwardly or downwardly from this position a taper in one direction or the other will be produced. The adjustment is effected by a rod 350 attached to the block 336 and having a screw thread engaging nuts 352, 356 on opposite sides of a cover 354 fixed to a casing 342 mounted on the housing 214. The nut 352 is rotatable directly by a wrench to adjust the rod 350 and the nut 356 is rotatable through a wrench-operated pinion 358 to lock the rod in adjusted position. A ring 370, Figs. 10 and 15, is secured by serrations 371 to rotate with the nut 352 and is provided with a cam 388 lying within a cage 378 having recesses 382, carrying balls 384. Graduated scales are marked on the ring 370 and cage 378 and are observable against a fixed index through an aperture in the cover plate 372. The graduations on ring 370 read in thousandths of an inch taper per inch and after one complete revolution of the ring the cam 388 engages one ball 384<SP>1</SP> which has been pressed into a groove 386 in the ring by a spring plunger 394. This releases the cage and allows it to rotate with the ring until the plunger snaps into the next recess 382, the corresponding ball entering the groove 386. The cage thus indicates hundredths of an inch of taper per inch and remains locked by the plunger 394 until the ring 370 has made another revolution. Since the adjusting rod 350 and the bar 328 must be parallel when adjusting the taper, and since the adjustments must be made from the diameter at the end of the cut for external threads and at the beginning of the cut for internal threads, the housing 342 is mounted adjustably on the housing 214 by means of screws 344 as shown in Fig. 20, this position being used for external threads. An index 428 on the housing 342 reads against a fixed scale 426 and registers with the zero of the scale when the head opens at the end of the cut, the bar 328 then being parallel to the rod 350, and the adjustment for taper is made in this position. For commencing the cut, the index 428 is brought opposite the graduations of scale 426 representing the required length of thread. For internal threading the housing 342 is inclined in the opposite direction to that of Fig. 20 and an index 432 reads against the scale 426, again being brought to the zero for setting the taper and to the required reading on the scale for commencing the cut. Lubricating die-heads.-An oil reservoir 400, Fig. 10, is formed in the cover 398 of the housing 214 and contains a number of wicks 406 leading to passages 406<SP>1</SP>, 406<SP>11</SP>, 409, 412 and 416, 417, Fig. 9, for respectively lubricating the trunnion 330, bar 328, pivot 332, shell 224 and the draw bar 196. Lubricant also passes through the bar 196 and radial passages 419, 419<SP>1</SP> therein, Fig. 3, to the stem 98 of the spider 100, and a further wick 402 leads to passages for lubricating the sliding movement of the cylinder 228 within the housing 214. Heavy lubricant is supplied by a fitting 96, Fig. 3, to each chaser slide 72 and proceeds by passage 94 to a groove 92 extending round the four sides of the slide so as to form a seal against swarf &c. Lubricant is also supplied through radial plugged passages to an annular chamber 154, Fig. 3, from which it proceeds through spring seals 159 to passages 161, 162 in the opposite sides of the slides 72, and also through axial passages 166, (Fig. 7, not shown), in the body 44 to grooves 170 on the cha