GB350516A - Improvements in and relating to machine attachments for holding screwing dies, screwtaps, and the like - Google Patents

Abstract

350,516. Screwing and tapping. CRAWSHAW, L. S., Standard Screw Works, Charles Street, Halifax, Yorkshire. Feb. 15, 1930, No. 5109. [Class 83 (iii).] Yielding-drive attachments.-A screwing die, diehead, tap, &c., is attached to the turret or toolpost, &c., of an automatic lathe by means of a friction clutch which slips continuously during screwing so as to cut at a reduced speed without the use of reduction gearing. The die, tap, &c., is carried in a holder 7 which is attached to a shank 1 by means of a screw-thread 11 of opposite hand to that of the die or by a cam preferably of helical formation. The holder is rotatable on the screw 11 within the limits of adjustable stops 9, 10 and the shank 1 is rotatable within a sleeve 2 secured to the turret &c. The shank and sleeve are connected by a yielding clutch, preferably consisting of plates 3, 4 splined respectively to the sleeve 2 and a second sleeve 5 keyed at 6 to the shank. In operation the die &c. is fed against the rotating work whereupon the holder 7 is screwed partly off the cam 11, thus giving the die a lead on the work and also imposing pressure on the plate clutch. The die then screws the work but rotates with it to some extent whilst the clutch slips, the amount of slip depending on the amount by which the feed of the die is less than the pitch of the thread being cut. On unscrewing the die, the holder returns to its normal position and stops 12, 13 are brought into engagement to effect a positive withdrawal or in the case of opening-dies the return is performed by a spring, cam, &c. The die may be carried by the sleeve 2 and the shank 1 secured to the turret and the die &c. may, be rotated whilst the work remains stationary. The stops 12, 13 may be replaced by a ratchet.