GB1102592A - Methods and apparatus for forming screw threads and screw threaded assemblies so formed - Google Patents

Abstract

1,102,592. Making threaded tubes; forging. WELLINGTON ENGINEERING WORKS Ltd. 1 June, 1965 [9 June, 1964 (2)], Nos. 23771 and 23772/64. Headings B3A and B3H. [Also in Division B5] An external thread is formed on a metal or synthetic resin tube by compressing the tube axially between dies while supported by a mandrel. The thread 98, Fig. 6, can be single- or multi-start and extends from an axial slot 96 previously formed in the tube. The end 97 of the tube is clamped within pivoted half-bushings 78 and 79 (Fig. 3, not shown) operated through levers 71 and 72 from an hydraulic cylinder 67. Between the tube end and bushings and attached to the bushings, are half dies 57 whose end faces 61, Fig. 4, combine to form a helical surface. Coaxial with the tube is an hydraulic ram 20 to which is attached, with the interposition of spacers 30, 32 and 35, and a collar 36, a mandrel 34 with a reduced end 40. Surrounding the mandrel and held within a sleeve 42 is a second die 45 which is of cylindrical form with its left hand end formed with a helical surface (Fig. 5, not shown) corresponding to the faces 61. As the ram 20 is moved to the left the mandrel enters the tube and the wall of the tube is forced into the space between the helical faces of the die ports 57 and 45. A pin 86 which co-operates with the axial slot in the tube for location purposes, is withdrawn from the slot during thread forming by the action of a cam follower 39 attached to the collar 36 pivoting a lever 53 operatively connected to the pin. The outer tube 100 (Fig. 8, not shown) of a scaffolding prop can conveniently be threaded in this manner, an inner tube 103 sliding within the tube 100, and a collar 109 being threaded on its end. Adjustment of the length of the prop is made by choosing an appropriate hole 105 for a pin 106 and finely adjusting the length by rotating the collar 109.