GB361050A - Improvements in or relating to method of and machine for producing screw threads in two oppositely disposed conical surfaces of a work piece - Google Patents

Abstract

361,050. Milling screws. SOKAL, S., 1, Great James Street, Bedford Row, London.-(Hasse & Wrede Ges., C. ; 116A, Christianiastrasse, Berlin.) Sept. 23, 1930, No. 28483. [Class 83 (iii).] In cutting screw threads on work-pieces having two oppositely disposed conical surfaces, such as pipe-couplings, a continuous thread over the apex of the conical surfaces is produced by two milling - cutters having annular series of teeth and acting simultaneously from both ends of the work, an axial feed equal to the pitch of the thread being given to the work. The work is mounted in a worm-driven chuck 18 rotatable on a head 17 which is angularly adjustable on a saddle 16 bv means of bolts and arcuate slots 26. The milling- cutters 12, 13 are rotatably carried by heads 7 transversely adjustable by means of cams and screws (not shown), on saddles 3 which are adjustable along ways 1 by racks and pinions 5 and handwheels 4. In operation, one cutter is adjusted longitudinally so that it projects several threads beyond the apex of one cone and the other cutter is adjusted to an exact pitch-distance therefrom by means of a gauge comprising a pin 8, Fig. 5, attached to a base 9 having a V-notch for engaging one cutter-spindle to set the< >pin 8 parallel thereto and a flat surface for engaging the other spindle. The length of the pin 8 is an exact multiple of the pitch of the thread being cut and each cutter terminates in a flat surface a passing through the outer base points of the last tooth. A scale 14, graduated in pitch divisions, is then adjusted along the head 7 until a pointer 15 secured to 'the bed registers with a graduation thereon, the scale then being secured to the head. The second cutter is next moved axially, after the gauge 8 has been removed, and the cutters moved laterally so as to clear each other, until its inner end projects beyond the apex of the work and the pointer 15 registers with a graduation on the scale 14, thus ensuring that the cutters will both produce the same helix on the work. The cutters are then Ted laterally until they contact with the work and are adjusted to the correct depth of cut by scales on the slides, adjustable stops being provided to limit the depth of cut after the initial adjustment. Chucks.-The chuck consists of a drum 18 carrying three concentric jaws 21 operated simultaneously by a toothed ring 24, right- and left-hand screws 22 and wedges 23, and also carrying three independent jaws 25. The jaws 21 are first actuated to grip the work lightly, the jaws 25 are then closed to grip the work lightly and prevent its distortion whilst the jaws 21 are tightened securely, after which the jaws 25 are also tightened.