Depressed center grinding wheel

Abstract

A depressed center grinding wheel comprises an abrasive disc. The abrasive disc comprises a working layer, an intermediate layer, a back layer, and at least two reinforcing scrims. The working layer comprises first abrasive particles retained in a first binder material. The first abrasive particles include from 40 to 100 weight percent of first shaped abrasive particles. The back layer comprises second abrasive particles retained in a second binder material. The second abrasive particles include first crushed abrasive particles and are essentially free of shaped abrasive particles. The intermediate layer is disposed between the working layer and the back layer. The intermediate layer comprises third abrasive particles retained in a third binder material. The third abrasive particles include 25 to 75 weight percent of second shaped abrasive particles.

1 - 13 . (canceled) 
     
     
         14 . A depressed center grinding wheel comprising an abrasive disc having a working surface and a back surface opposite the working surface, wherein the working surface has a depressed center portion, and wherein the abrasive disc comprises:
 a working layer comprising first abrasive particles retained in a first binder material, the first abrasive particles comprising first shaped abrasive particles, wherein the first shaped abrasive particles comprise from 40 to 100 weight percent of the first abrasive particles;   a back layer comprising second abrasive particles retained in a second binder material comprising first crushed abrasive particles and essentially free of shaped abrasive particles;   an intermediate layer disposed between the working layer and the back layer, the intermediate layer comprising third abrasive particles retained in a third binder material, the intermediate layer comprising second shaped abrasive particles and second crushed abrasive particles, wherein the second shaped abrasive particles comprise 25 to 75 weight percent of the second abrasive particles;   a first reinforcing scrim sandwiched between the back layer and the intermediate layer; and   a second reinforcing scrim adjacent one of:
 the back layer opposite the intermediate layer; 
 the intermediate layer opposite the back layer; or 
 the working layer opposite the intermediate layer. 
   
     
     
         15 . The depressed center grinding wheel of  claim 14 , wherein the second reinforcing scrim is sandwiched between the working layer and the intermediate layer. 
     
     
         16 . The depressed center grinding wheel of  claim 15 , further comprising a third reinforcing scrim bonded to the working layer opposite the intermediate layer. 
     
     
         17 . The depressed center grinding wheel of  claim 14 , wherein the second reinforcing scrim is secured to the back layer opposite the intermediate layer. 
     
     
         18 . The depressed center grinding wheel of  claim 17 , further comprising a third reinforcing scrim sandwiched between the intermediate layer and the working layer. 
     
     
         19 . The depressed center grinding wheel of  claim 17 , further comprising a fourth reinforcing scrim bonded to the working layer opposite the intermediate layer. 
     
     
         20 . The depressed center grinding wheel of  claim 14 , wherein the first shaped abrasive particles comprise triangular shaped abrasive particles. 
     
     
         21 . The depressed center grinding wheel of  claim 14 , wherein the second shaped abrasive particles comprise triangular shaped abrasive particles. 
     
     
         22 . The depressed center grinding wheel of  claim 14 , wherein the ratio of the weight percent of the first shaped abrasive particles in the first abrasive particles to the weight percent of the second shaped abrasive particles in the second abrasive particles is from 40:60 to 60:40. 
     
     
         23 . The depressed center grinding wheel of  claim 14 , wherein the ratio of the weight percent of the first shaped abrasive particles in the first abrasive particles to the weight percent of the second shaped abrasive particles in the second abrasive particles is from 45:55 to 55:45. 
     
     
         24 . The depressed center grinding wheel of  claim 14 , wherein the first and second shaped abrasive particles comprise alpha alumina. 
     
     
         25 . The depressed center grinding wheel of  claim 14 , further comprising a centrally disposed arbor hole extending through the abrasive disc. 
     
     
         26 . The depressed center grinding wheel of  claim 14 , further comprising an attachment member centrally disposed on the back surface of the abrasive disc.