Patent GB-856231-A (GB)
Title: Cutting tool and method of making the same
IPC: B24D15/02
Filed: 1958-06-06
Abstract: 856,231. Making abrasive cutting tools, saws and files; brazing. SKIL CORPORATION. June 6, 1958 [Aug. 7, 1957 (2)], No. 18098/58. Classes 83 (2) and 83 (4). [Also in Group XXIII] A cutting tool comprises a metal base member and a multiplicity of cutting elements brazed thereto, the cutting elements being fragmentary particles comprising carbide cutting material distributed in single particle layer. The tool may be a disc surface finisher having a steel base 20, Fig. 1, with fragmentary particles of tungsten carbide, silicon carbide, boron carbide or crushed sintered cobalt cemented tungsten carbide brazed thereto by a layer of brazing metal, e.g. copper or silver alloy having a thickness less than half, preferably less than 10%, e.g. 2-5%, the average height of the particles. The particles may have a size range of 16-240 mesh, may be distributed in random fashion or in a regular pattern and the ratio of the area of the tool covered by the particles to the total area of the tool should be less than 1: 5, e.g. 1: 10. The tool may alternatively be a rotatable disc for sawing and surface finishing having cutting particles on both side surfaces and on the periphery. The particles on one side may be smaller than those on the other side which are smaller than those on the periphery. The tool may be a rectangular file or a conical file. Fig. 4, or may comprise a resilient steel strip 60, Fig. 5, shaped to fit a vibration type finisher. In manufacturing the tool the base member may be degreased and grit blasted and brazing material in metal or oxide form is electroplated or chemically deposited thereon or applied thereto by spraying, the silk screen process, brushing, rolling, wiping or dipping as comminuted metal or oxide dispersed in polyvinyl acetate, glycerine, ethylene glycol or methyl cellulose in the ratio of 80-60 to 20-40 brazing metal or oxide to vehicle. The cutting particles are distributed on the base by shaking and vibrating machines, vacuum pick-up and transfer devices, by electrostatic action or by sprinkling from a salt shaker. The fragments are then rolled or pressed lightly into contact with the base. Alternatively, the fragments may be first sprinkled on the base having tacky ethylene glycol or polyvinyl acetate thereon and the base then coated with a suspension of metal or metal oxide or the fragments may be coated with comminuted copper or copper oxide in a vehicle, e.g. ethylene glycol and then sprinkled on the base which may be coated with a tacky volatizable material. The tool is then heated in the non-oxidizing atmosphere of a conveyerized furnace to firstly cause sintering of the metal or oxide (if applied in comminuted form) and then to cause fusion thereof. Some anhydrous borax may be used with the brazing metal. In an example, a soft steel disc is sprayed on one side with copper oxide powder (67.5%) in ethylene glycol (32.5%), crushed sintered cemented tungsten carbide of grit size No. 36 is sprinkled on the coated surface, a wooden disc is used to press the particles down and the assembly is passed through a protective atmosphere furnace having a preheat zone 400-1900‹ F., a brazing zone 2040‹ F. and a cooling zone 200‹ F. In another example, a mild steel disc is coated on its periphery and on one side with brazing material and crushed sintered cemented tungsten carbide and heated to effect brazing and then the other side is similarly coated but with smaller particles and then heated to effect brazing. It is stated that the following cutting tools may be produced machine oscillating plates; hand sanding blocks machine rotating rods or tubes; power files ; jig-saw cutting wire; flexible sander plates belts or strips for circular drums in wood, leather or plastic working and continuous sanding belts.