Patent GB-498779-A (GB)
Title: Improvements in or relating to thread cutting machines
IPC: B23G5/12
Filed: 1938-02-21
Abstract: 498,779. Screwing die-heads ; taps. LANDIS MACHINE CO. Feb. 21, 1938, No. 5452. Convention date, Nov. 9, 1937. [Class 83 (iii)] A taper thread-cutting machine comprises a sleeve slidable within the tool body and enclosing an axially adjustable plunger carrying cams associated with radially adjustable cutters on the tool head, and a slidable work contacting ring which operates an axial cam bar to cause relative movement between the plunger and the sleeve as the operation proceeds to give an automatic radial adjustment of the cutters during the cutting of the thread. The body 1 is keyed to a head 2 having radial T slots in which slide chaser assemblies 6 having ribs 13 guided in inclined grooves 12 of a central expanding cam 11 slidably keyed in the head. The cam 11 is secured to a plunger 9 mounted within a collapsing sleeve 8 slidable in the body. Transverse gibs 17 secured in the sleeve 8 pass through a slot 16 in the plunger and serve to guide a transverse cam bar 19 having inclined grooves 21 coacting with lugs secured to the walls of slot 16. A control collar 24 slidable on the body carries an adjustable cam slide 26 coacting with the bar 19 so that longitudinal movement of the collar operates the cam slide to reciprocate the plunger within the sleeve and imparts radial movement to the chasers. The control collar carries an oil shroud which receives oil through passages 31 and also carries a work-contacting ring 28. During threading the plunger 8 is held rigidly. The slide 26 is pivoted at 39 and its other end is adjustable by means of arcuate slots 41. The head of the adjusting bolt 40 has an index mark coacting with graduations on a cover plate over the slots 41, the graduations showing directly the degree of taper produced by the slide setting. A modified form of adjustment is described wherein the bolt 40 carries a locking washer having lugs coacting with spaced grooves to set the taper, and fine adjustment being obtained by means of a calibrated eccentric bushing surrounding the bolt 40. In operation the ring 28 engages the face of the work and as the threading proceeds the collar 24 is moved to the right, thus operating the bar 19 to impart any required taper to the thread between <3>/16 and ¥" per foot. The size adjustment is obtained by movement of the sleeve 8 which communicates movement to the plunger 9 through bar 19 and lugs 22. For this purpose the sleeve has fine threads 62 engaging in an adjusting nut 63 which is itself coarse threaded at 64 to a latching nut 66, which receives the headed stud 72 clamped by a nut 73 to a seating on a latching element 71. The stud 72 locks the sleeve 8 against movement to the left during operation. By rotating the nut 63 by means of openings 76 a differential screw action is obtained for longitudinal adjustment of sleeve 8 which movement is communicated through the bar 19 to plunger 9. Serrations 79 coacting with a detent 80 are provided on the nut 63, a rotation through one serration producing a radial chaser adjustment of À001". The window 77 is of specified peripheral length calculated to give definite diametrical adjustment for different tapers and calibrations on the body indicate the effect on the gauge lengths of the thread being cut by different diametrical increases or decreases. During cutting, a spring tends to move the sleeve 8 to the right, this movement being prevented by an arcuate latch 68 located between a flange 67 and latch seat member 71. The control collar carries a graduated bar which may be adjusted longitudinally according to the length of thread desired. At a predetermined point a roller 93 on the bar engages a plunger 87 to force the latch from its seating and allow the spring to move the sleeve 8 to the right until latch member surface 94 engages the seat 96 of member 71. This causes withdrawal of the chasers from the work. An adapter 33 for attachment to a machine is secured to the body 1. For resetting the tool a hand crank 123 is rotated to operate rack and pinion mechanism 113, 114 to return the collar 24 to the right, compress the spring 81, and reset the latch mechanism. In order to remove the chasers, the collar 24 is moved back by the crank 123 and a screw 53 turned to separate the cam 11 from the plunger 9. The projections 13 or the chasers may then be released from their grooves in the cam 11 and the chasers withdrawn. The collar is held during this operation by a pin which locks the crank mechanism. The chaser 134, Fig. 13, is held against a supporting member 140 by a screw 138 threaded into a bushing 139 and operating as described in U.S.A. Specification 2,120,621.