GB1218985A - Improvements in and relating to cutting tools and processes - Google Patents

Abstract

1,218,985. Broaching; generating; grinding. MINISTER OF TECHNOLOGY. 20 May 1969 [20 Feb., 1968], No. 8181/68. Headings B3C, B3D, B3K, B3L and B3T. A method of machining in or on a workpiece, comprises rotating a cutter or grinding wheel of non-circular multi-arc form about its axis, and either rotating the workpiece about an axis parallel to and fixed relative to the cutter axis and in the same direction at a related speed, or giving the two the same relative motion by turning the axis of the cutter in the opposite direction around the workpiece axis. When machining a square bore of side 2l, and diagonal 2R, Fig. 4a, the multi-arc cutter has a length R, is rotated about its axis B at twice the rotational speed of the workpiece about its axis A. The machining could be carried out by fixing the workpiece and causing axis B to travel about axis A in reverse direction in a circle of radius ¢R. Four such cutters may be used, Fig. 6 (not shown). A regular hexagonal bore may be produced by a cutter having 3 arcs, Fig. 5a, or three such cutters, Fig. 7 (not shown), may be used. In general, a cutter with N arcs will produce a figure having 2N sides if the 2: 1 ratio of rotational speeds is maintained. The cutters may be of oval form, Fig. 8 (not shown). A double square, Fig. 9 (not shown), or a double hexagon, Fig. 10 (not shown), may be produced by two cutters. A male workpiece can be produced by an identical or complementary shaped cutter, Figs. 1 and 2 (not shown). A tool for cutting a square hole comprises a spindle 1, Fig. 12, for attachment to a drilling machine, upper and lower crossheads 2, 3 secured together and carried by spindle 1. Cutter spindles 7, 8 rotatable in the crossheads and carrying gears 11, 12 which mesh with an internal gear 10b so that the cutter spindles rotate at twice the speed of spindle 1. A single cutter may be used, in which case spindle 7 is replaced by a balancing rod. In a modification, spindle 17 carries a roller of diameter "l" which rolls inside a like-sized bore in a jig under the workpiece. In a further modification, an adjustable tool for cutting square bores of different sizes comprises a turn buckle 25, Fig. 13, so as to vary the radial positions of cutter spindles 7, 8. The cutters may have end cutting edges. They may be used in a jigging type machine which provides for reciprocating movement of broach type cutters as well as rotation. It is stated that an external hexagonal shape can be generated by using six equally spaced cutters.