GB356228A - Improvements in or relating to screw cutting chasers - Google Patents

Abstract

356,228. Chasers. JONES & LAMSON MACHINE CO., Springfield, Vermont, U.S.A.-(Assignees of Bysshe, E. T. ; 91, Summer Street, and Finn, R. R. ; 98, Wall Street, both in Springfield, Vermont, U.S.A.) April 29, 1930, No. 24158/31. Convention date, May 15, 1929. Divided on 356,186. [Class 83 (iii).] A screw-cutting chaser of the tangent type has a series of ratchet serrations on one of its side faces to gauge the extent of grinding during sharpening and to facilitate the resetting of the chaser in a die-head. The chaser 1 has a surface 2 for engagement with a corresponding plane surface on the head and is provided with a dovetailed projection 5 accurately ground and lapped to fit the head. Accurately formed serrations of ratchet form 6 are provided on the rear portion of the projection 5 and constitute the gauging elements, the amount ground off the cutting end of the chaser, together with that worn away, being made equal to the distance between the serrations so that on re-setting the chaser in the head, the next succeeding serration to that previously used will place the cutting edge in the same relation to the work as before grinding. The operative face of the chaser is grooved longitudinally at 3 to provide ridges of the correct thread profile, the ridges being inclined to the face 2 at the correct helix angle of the thread and the first ridges being cut away by progressively smaller amounts, as at 7, to distribute the cut, and the remaining ridges serving to guide the chaser on the finished thread. The chaser may be used in a die-head as described in Specification 356,223.