GB542475A - Improvements in or relating to devices for butting or trimming screw threads, more particularly in the manufacture of screw gauges - Google Patents

Abstract

542,475. Milling screw-threads. MOLLART ENGINEERING CO., Ltd., and HARRIS, S. E. July 22, 1940, No. 12004. [Class 83 (iii)] [Also in Group XXIII] In a machine for trimming off the partly formed screw thread at the end of a plug or ring gauge, the work piece is given a helical motion of one turn or less relatively to a grinding-wheel or milling-cutter the axial component of the movement being produced by a helical cam surface co-acting with an adjustable follower. A motor 11 driving the grinding-wheel or milling- cutter 12 is mounted on compound hand-adjusted slides 13, 14. The work spindle 17 carrying a faceplate 34 on which a ring gauge 35 is mounted in bearings 20, 21. and is urged to the right in Fig. 2 by a spring 22 located between a washer 43 and a washer 41 engaging a sleeve 39 pinned to the spindle at 40. The spindle carries a cam 23 having a surface 24 generated by a radial line 24a which rotates round the spindle axis to position 24b while gradually increasing its inclination to a transverse plane. The cam is engaged by a roller 25 which is radially adjustable in a bracket 30 which may be graduated in pitch sizes or threads per inch. Thus as the spindle is rotated by a hand-wheel 18 the spindle is moved axially by an amount depending on the setting of the roller 25. The starting position is determined by the engagement of the pin 40 with a fixed projection 44 and the end of the operative movement by an adjustable member 45 on the hand wheel engaging projection 44. In a modification the surface of the cam member may be grooved, each groove corresponding to a definite pitch, or the cam may be formed with steps. Alternatively, the cam may be double-sided, opposite sides being used for threads of opposite hands or if the required rotation of the work spindle is less than 180 degrees the cam member may have two portions on the same face adapted for threads of opposite hand. The wheel engages the work as shown in Fig. 4. In some cases the spindle may be driven by power.