Patent GB-462412-A (GB)
Title: Improvements in and relating to screw-cutting die heads
IPC: B23G5/12
Filed: 1936-01-27
Abstract: 462,412. Screwing die-heads. TRIGGS, W. W. (Landis Machine Co.) Jan. 27, 1936. No. 2573. [Class 83 (iii)] A self-opening screwing die-head having radially movable chasers and carriers such as those described in Specification 425,932, has a front unit comprising a chaser-carrying body, a closing ring and a locking ring, and a rear unit comprising a supporting member on which the front unit is adapted to slide forwardly for unlocking the locking ring, spring means being provided between the locking ring and the supporting member so as to return the front unit to its normal position on the support after the head has been opened. The head comprises a shank or support 10, Figs. 2 and 16, for mounting on the carriage of a turret lathe &c. and having a hollow boss 43 on which the body 11 is axially slidable. Dovetailed recesses 18 on the front face of the body receive carriers 12 for tangential chasers 13 which are adjusted by screws 22 and secured by clamps 20 (not shown). The carriers 12 have bevelled surfaces 31 for co-operation with projections 30 on a closing ring 14 axially slidable on the body 11, ribs 33 on the carriers engaging grooves on the projections for positive opening of the head. Springs 37 located in pockets in the body 11 and ring 14 tend to force the ring rearwardly relatively to the body into the open position but the ring is locked in the cutting position by means of projections 41, Fig. 5, on a locking ring 15 engaging projections 38 on ring 14. The ring 15 is rotatably mounted on a flange 45 of the shank 10 and rotation of the body 11 on the shank is prevented by keys 25 thereon sliding in grooves 26 in the shank. The projections 30 on the closing ring 14 pass through slots in the body to prevent rotation of the ring. The ring 14 is axially adjustable on the body to vary the diameter of thread cut by the head by means of a ring 17 screwing on the body at 28 and having a flange 61 engaging a flange 51 on the ring 15. During cutting of a thread the body 11 and the rings 14, 15 and 17 are held in the rearward position shown in Figs. 2 and 5 by means of springs 59 engaging the bases of pockets in the ring 15 and surrounding headed pins 57 attached to a ring 16 abutting against the flange 45 of the shank 10, but when the desired length of thread has been cut, relative feed between the die-head and work is stopped and the body, together with the rings 14, 15 and 17, moves forward against the pressure of the springs 59. Whilst moving forwards two radial pins 56, Fig. 10, on the ring 15 engage cam surfaces 47, Figs. 10 and 16, on the sides of slots 46 in the shank flange 45, thereby rotating the ring 15, so that bevelled surfaces 39, 40 on the projections of the rings 14, 15 respectively may cause further rotation of the ring 15 until the projections 38 on the ring 14 are opposite recesses in the ring 15, whereupon the springs 37 force the ring 14 rearwardly and open the head, as shown in Fig. 10. When the chasers are clear of the threads on the work the springs 59 draw back the body 11 and rings to abut against the ring 16 as shown in Fig. 5. To reset the head the ring 16 is rotated by hand or by a cam acting on a lever 66 thereon to cause the bevelled surfaces 39, 40 to force the ring 14 forwardly against the pressure of the springs 37 until the projections 41 snap behind the projections 38, thereby locking the ring 14 in the cutting position. For cutting left-hand threads the carriers 12 are replaced by left-handed carriers but the chasers and remaining parts of the head are unchanged. The adjusting ring 17 is locked in position by means of a radial screw projecting through a lug on the body 11.