GB330767A - Improvement in screw threading dies - Google Patents

Abstract

330,767. Fairweather, H. G. C., (National Acme Co.). June 13, 1929. Screwing-dies and dieheads. - In a self-opening die-head the chaser carrying body is axially movable, within a. closing cap and is driven from a centrad shank by meano of interengaging lugs on the body and shank which allow relative axial movement. The closing cap 1 has circumferential cam surfaces 16, Figs. 1 and 3, co-operating with similar surfaces 15 on the chasers 7 for adjustment of the latter by rotary movement of the cap under control of two tangential screws in the cap engaging lugs 35 on a ring 29 which carries an axial pin passing into an opening in the rear wall of the body 2. Graduations on the ring 29, visible through an aperture in the cap, facilitate adjustment. The chasers are attached by screws 11 and pins 12 to blocks 8 sliding in radial guides in the body 2 and are provided with bevelled surfaces 17 for co-operation with the front edge of the cap 1 to open and close the head. Radial springs 14 assist in opening the head. The rear surface of the body is provided with radial recesses 18, Figs. 1, 2 and 16, which receive driving lugs 19 on the shank 3, the recesses being deeper than the lugs to allow relative axial movement of the body and shank and springs 23 normally serving to draw the body and shank together through a ring 20 attached to the body by screws 20<a>. A hand lever 25 is pivoted at 28 to a socket 26 secured to the cap 1 by screws 27 and engages a slot in the body 2 for re-setting the chasers. In operation, with the die-head closed and the springs 23 maintaining the lugs 19 in contact with the rear of the body 2, the, action of screwing draws the head as a whole along the work. When the desired length of thread has been almost completed further motion of the shank 3 is prevented by a stop on the machine and the body is drawn forwards, against the springs 23, to the position shown in Figs. 3 and 16. In this position the bevelled surfaces 17 on the chasers are just clear of the cap 1, whereupon the chasers may spring radially outwards and force back the cap. Simultaneously with this movement the springs 23 draw back the body and chasers axially so as to close the sgace 21<a>, Fig. 16, and, thus allow the chasers to cut, close up to a shoulder on the work without damage. The head may be re-set by hand or by causing the lever 25 to engage a stop on the machine during rearward movement of the head. Removal of the lever 25 with its socket 26 enables the head to be taken apart for cleaning and for a rotary die-head, the lever 25 is replaced by a yoke engaging a grooved collar at the rear of the cap. Cuttings, catching and removing.-The adjacent ends of the bores in the body 2 and shank 3 are oppositely bevelled at 6 and 5 respectively to allow free axial movement between the body and shank in spite of the presence of chips &c. Specification 228,589 is referred to.