GB579523A - Improved method, and tools employed therewith, for cutting articles out of sheet metal or plywood blanks - Google Patents

Abstract

579,523. Cutting-out presses. WARBURTON, C: L., WILSHAW, F. H., METROPOLITANVICKERS ELECTRICAL CO., Ltd., and'CROSLAND, Ltd., W. May 15, 1944, No. 9317. [Class 31 (i)] [Also in Group XXII] A press tool for punching blanks from sheet metal or plywood comprises a support of mainly non-metallic material which is hard; capable of being sawn and having a specific gravity greater than unity, in which support is sawn a slot in which is inserted a steel strip or rule to the extent of at least 75 per cent. of its depth, the protruding part of the rule being sharpened to a fine edge. The invention is illustrated as applied to a tool for punching out annular washers. A block of supporting material 1 is sawn as shown in Fig. 2 to form two concentric slots 6, 7 with bridging gaps 5. Steel rules are embedded in the slots' as shown in Fig. 4, the rear edges of the rules being slotted to bridge the gaps 5. Preferably the cutting edge is bevelled mainly on one side to minimise the tendency of the sheet or blank to bulge. The cutting edge may be finished by honing or diamond grinding. Rubber pads 10, 11 and 12 are used as ejectors or alternatively the support may be recessed to accommodate springs. Suitable materials for the support or backing are highly compressed plywood bonded between plies with a hard-setting synthetic resin which may be reinforced with thin metal laminae or the resinised composition known under the Registered Trade Mark "Traffolyte." The tool. may be used with a steel platen which may. be covered with rubber if a slight inward flanging- of the edges of the blank is required.