Coated abrasive disc

Claim 1

A self-supporting grinding disk for mounting on the shaft of a power tool for rotation, the disk having an abrasive grinding face for parallel grinding and a peripheral edge for edge grinding comprising: a round disk body of thermoplastics material, said disk body having a central hub portion for securing the disk to a shaft and a flexible workpiece-contour-following portion outwardly of the hub portion; a layer of thermosetting plastics resin which contains abrasive grit coated directly on the disk body to comprise the grinding face of said grinding disk, the plastics resin being curable at a temperature of less than 125° C. and cured, the thermosetting plastics resin being compatible with the thermoplastics material of the disk body and being bonded and adhesively fused thereto; the thickness of the disk body outwardly of the hub being between five one thousandths and fifty one thousandths of an inch; the diameter of the disk body being no more than four inches; the disk body having a coefficient of linear thermal expansion between 0.00005 and 0.0001 inch per inch per degree centigrade as tested by the A.S.T.M. testing standard D 696-79; the disk body being composed substantially of a polyamide thermoplastic material and having a deflection temperature under flexural load of 264 psi of between 125° F. and 350° F. according to the A.S.T.M. testing standard D648-82; the disk body having a melting point to withstand the heat of grinding friction in parallel grinding operations but to be smoothly and continuously heat disintegratable at the same rate as the layer of thermosetting plastics resin which contains the abrasive when the periphery of the grinding disk is used for edge grinding a work piece whereby to present fresh grinding abrasive to the work piece as the diameter of the disk decreases.