Cup type grinding wheel

Abstract

Cup type grinding wheel to be attached to a rotary tool includes a plastic base plate made of a glass fiber-reinforced plastic, a metal annular plate with pieces of grindstone on a fixing surface of the metal annular plate, and fasteners for integrating the plastic base plate with the metal annular plate. Heads of fasteners are positioned at the same level as the fixing surface or at a lower level than the fixing surface toward the plastic base plate.

What is claimed is: 
     
         1 . A cup type grinding wheel having a recessed portion formed by a projection of a central part of a plastic base plate like a circular plate to dispose a plurality of pieces of grindstone, and the cup type grinding wheel enabling to be attached to a drive mechanism of a rotary tool through an attachment hole formed in a central plane of the recessed portion, comprising:
 the plastic base plate made of a glass fiber-reinforced plastic in which a nylon resin is reinforced by glass fibers, and including
 amounting surface like a flat plate to dispose the plurality of pieces of grindstone, 
 a slant surface of the recessed portion connected with the mounting surface and having a predetermined angle of slope, and 
 the central plane of the recessed portion connected with the slant surface and forming the attachment hole therein; 
   a metal annular plate of a metal plate formed in an annular shape including
 an abutting surface abutting on the mounting surface, and 
 a fixing surface fixing the plurality of pieces of grindstone on an opposite side to the abutting surface; 
   the plurality of pieces of grindstone fixed at a periphery of the fixing surface at a predetermined interval; and   a plurality of fasteners passing through the mounting surface and the fixing surface at positions except positions of the plurality of pieces of grindstone so that the plastic base plate and the metal annular plate are integrated with each other,   wherein the plurality of fasteners are disposed at a predetermined interval in a circumferential direction of the mounting surface and the fixing surface and integrate the plastic base plate with the metal annular plate so that a head of each of the plurality of fasteners is positioned at the same level as the fixing surface of the metal annular plate or at a lower level than the fixing surface toward the plastic base plate.   
     
     
         2 . A cup type grinding wheel as claimed in  claim 1 , further comprising an elastic sheet like an annular plate made of an elastic material between the mounting surface and the abutting surface. 
     
     
         3 . A cup type grinding wheel as claimed in  claim 2 , further comprising a cylindrical sleeve disposed to let both through holes of the plastic base plate and the elastic sheet communicate with each other which through holes each of the plurality of fasteners passes through, each of the plurality of fasteners passing through the metal annular plate and the sleeve to integrate the plastic base plate, the elastic sheet and the metal annular plate with each other. 
     
     
         4 . A cup type grinding wheel as claimed in  claim 1 , wherein each of the plurality of fasteners is a rivet. 
     
     
         5 . A cup type grinding wheel as claimed in  claim 2 , wherein each of the plurality of fasteners is a rivet. 
     
     
         6 . A cup type grinding wheel as claimed in  claim 3 , wherein each of the plurality of fasteners is a rivet. 
     
     
         7 . A cup type grinding wheel as claimed in  claim 2 , wherein each of the plurality of fasteners is a rivet, a body of the rivet having a small-diameter part passing through the metal annular plate and a large-diameter part passing through the plastic base plate and the elastic sheet so that a shoulder is formed between the small-diameter part and the large-diameter part. 
     
     
         8 . A cup type grinding wheel as claimed in  claim 1 , wherein each of the plurality of pieces of grindstone is fixed on the fixing surface by firing to integrate them. 
     
     
         9 . A cup type grinding wheel as claimed in  claim 2 , wherein each of the plurality of pieces of grindstone is fixed on the fixing surface by firing to integrate them. 
     
     
         10 . A cup type grinding wheel as claimed in  claim 3 , wherein each of the plurality of pieces of grindstone is fixed on the fixing surface by firing to integrate them. 
     
     
         11 . A cup type grinding wheel as claimed in  claim 4 , wherein each of the plurality of pieces of grindstone is fixed on the fixing surface by firing to integrate them. 
     
     
         12 . A cup type grinding wheel as claimed in  claim 5 , wherein each of the plurality of pieces of grindstone is fixed on the fixing surface by firing to integrate them. 
     
     
         13 . A cup type grinding wheel as claimed in  claim 6 , wherein each of the plurality of pieces of grindstone is fixed on the fixing surface by firing to integrate them. 
     
     
         14 . A cup type grinding wheel as claimed in  claim 7 , wherein each of the plurality of pieces of grindstone is fixed on the fixing surface by firing to integrate them.