GB658488A - Self-opening screw-cutting dieheads - Google Patents

Abstract

658,488. Screwing die-heads. HERBERT, Ltd., A., LLOYD, A. H., and MALLINSON, H. Nov. 17, 1949, No. 29406. [Class 83 (iii)] A self-opening die-head of the kind in which a chaser adjusting ring 17 is held in the closed position by a spring-pressed detent pin 30 which is slidably carried by the slidable body 12 of the die-head and is engaged with an abutment 35 on the flange 14 of the shank 11 of the die-head so as to be held against axial movement when the shank and work-piece are so held at the end of a screw-cutting operation whereby continued axial movement of the body 12 due to the engagement of the chasers 16 with the work-piece withdraws a tooth 37 of the ring 17 from engagement with the pin 30 to allow a spring 22 to move the ring 17 angularly so as to withdraw the chasers is characterized in that the tooth is detachably mounted and positioned by means of oppositely-disposed screws 41 in the ring 17 which engage a pin 39 on which the tooth is carried. The tooth is slidingly fitted in an annular groove 21 in the ring 17, being held therein by means of a plate 18 connected to the body 12. The pin 30 is mounted for angular movement in a bush of the plate 18 and is provided with oppositely-disposed faces 38 spaced by different amounts from the axis of the pin selectively to coact with the tooth for roughing and finishing cuts. In operation, when the diehead has been set up with its shank supported by a slide, the latter is moved towards the work-piece to cut a thread thereon. When the threading operation, e.g. the roughing cut, has been completed, the axial movement of the shank is arrested but the engagement of the chasers with the work-piece causes the body 12 to travel onwardly, thus drawing the tooth away from the operative end of the pin 30, the latter being held against axial movement by its head 33 engaging the flange abutment 35. When the tooth is clear of the pin 30, the spring 22 turns the ring 17 to withdraw the chasers and the free end of the pin 30 engages the side face of the tooth 37, i.e. behind the latter. A stop 42 limits the opening movement of the ring 17. On the withdrawal of the slide, the die-head can be closed by manipulating the handle 44, the ring 17 having axially-extending helical projections engaging grooves in the chasers. Alternatively, the die-head may be provided with an additional sleeve for automatically closing the ring 17. When the side face of the tooth 37 has moved clear of the free end of the detent pin, springs 26 return the slidable body 12 axially towards the flange 14 and the die-head is maintained closed by the engagement of the pin 30 with the tooth 37. After a roughing cut, the detent pin is turned angularly through 180 degrees to bring its other face 38 into contact with the face 36 of the tooth 37 and a finishing cut taken on the work-piece. Specification 219,424, [Class 83 (iii)], is referred to.