GB327004A - Improvements in method of making screw thread dies and other similar articles - Google Patents

Abstract

327,004. Bath, J. March 22, 1929. Screwing-dies are formed by first finishing and hardening a die block and then forming parallel grooves in the block from the solid hardened metal by repeated grinding operations. In a machine for carrying out this method a profiled grinding-wheel W is mounted on a spindle 20 driven from a motor 32 and mounted on a vertical slide 22 which may be adjusted by a screw 25 operated by a hand-wheel provided with a graduated head. The die D is mounted on a slide 33 which is carried on a cross-slide 35 moving over ways 36 and actuated by a hydraulic cylinder 62. The feed of the block longitudinally of the grinding- spindle is effected by a screw 40 which may be rotated by change gearing 43 - - 46 operated by an arm 47 provided with a handle 50. The arm 47 carries a spring plunger 51 coacting with a stop 52. The gearing is so arranged that, when the arm is rotated through one revolution after first withdrawing the plunger 51, the block D is fed through a distance equal to the pitch of the gears to be cut. The die block is mounted on a magnetic chuck 63 and is accurately positioned against a stop 71 by means of a gauge bar 65 having projections 66, 67, the projection 66 being engaged with the edge 69 of an angle block 68 and the other projection being spaced from this edge by precision gauge pieces 70 according to the inclination of the grooves to be ground. The grinding-wheel is trued by means of tools 72, which may operate in the manner described in Specification 327,003, [Class 60, Grinding or abrading &c.], the amount of material removed from the wheel being accurately indicated and being compensated by lowering the grinding- wheel. In order to measure the depth of the thread a round wire 74 of determined diameter is placed in the thread groove and the distance between the bottom of the block and the top of the wire is measured by a micrometer 75. The wheel is lubricated during operation by fluid directed irom a pair of nozzles 76. In operation the finished and hardened blank is placed in position and the table reciprocated while the wheel is gradually fed downwards until the desired depth of thread is attained. The wheel is then raised and the arm 47 rotated to move the die block through one pitch, the grinding operation being repeated until all the grooves are cut. Finally a finishing cut is taken over all the grooves so as to bring the grooves to a uniform depth.