GB839401A - Improvements relating to cutting or abrading tools - Google Patents

Abstract

839,401. Making cutting-tools; shearing; shear-blades; milling-cutters. SIMMONDS AEROCESSORIES Ltd. June 17, 1958 [July 11, 1957], No. 22018/57. Classes. 83 (2),.83 (3) and 83(4). [Also in Group XXIII] A method of making a cutting element by slitting hardenable sheet-metal and displacing one edge of each slit to form a cutting-edge, wherein each cutting-edge is produced in at least two separate punching, operations, the first operation deforming a portion of the sheet towards one side thereof and the second operation shearing away a. section of said portion to provide an edge, the position of the remaining part in relation to the sheet is unchanged during shearing. A mild-steel strip 3 is fed intermittently through a two-stage punching machine, first-stage punches 4 and dies 5, Fig. 1, acting to slit the strip and form a series of tongue-portions 8, the tongues being staggered in adjacent rows. Second-stage punches 17 coact with dies 15, Fig. 3, to shear off each forward-edge part 9 of the tongues, and so form cutting-edges 25. The resulting edges have a clearance.angle c of about 30 degrees and an edge projection D of 0.04 ins. An edge projection of 0.02 ins. may be obtained by inclining each tongue from root to tip in the first punching stage, after which each tongue is sheared off, halfway along its length. Positive rakeangles R<SP>1</SP>,Fig. 5, are obtained either by punching on an incline or by displacing the edge 25 back towards the strip 3. In a modification, the edge 25 is displaced further back towards the strip 3 than the final required position, the edges are ground parallel to the strip, and finally the edge is again displaced away from the strip to give a clearance-angle of 10 degrees, a rake-angle of 15 degrees and an edge-projection of 0.015 ins. In a further modification the first-stage punches 41 and dies 44, Fig. 8, form deformations 45, and the second-stage punches 48, Fig. 9, remove the apices of the deformations, after which the tongues 49, 50 are displaced back towards the strip by different amounts so that edge 52 forms the cutting-edge and the tongue 50 forms a rubbing surface. The clearance and rake angles are each about 15 degrees. Alternatively the punches may be inclined or may be eccentric to the apex, and ground-edges may be provided as before described. The formed-strip may be bent half-round or formed into a drum. Disc-form cutting elements may also be produced.