Grinding head assembly

Claim 1

A grinding head assembly comprising: a. a backing plate holder adapted to be drivingly connected for rotation with a drive shaft, said backing plate holder having a downwardly facing annular plane surface substantially perpendicular to the axis of rotation of said drive shaft and an outermost peripheral edge symmetrically oriented about said axis; b. an annular backing plate having an upwardly facing annular plane surface and an outer flange extending upwardly from said backing plate annular plane surface, said outer flange having an exposed outer sidewall and an internal sidewall defining an upwardly facing backing plate holder receiving cavity; said outer flange having a plurality of upwardly facing notches disposed thereon c. an annular grinding wheel permanently mounted to an underside of said plane surface of said backing plate and having an inner wall; and d. means for fastening said outer flange of said backing plate to said peripheral edge of said backing plate holder including threaded securing means abuttable against said backing plate flange exposed outer sidewall extending through said upwardly facing notches and securable to said peripheral edge of said backng plate holder for urging said backing plate flange internal sidewall into tight frictional engagement with said backing plate holder outer peripheral edge, e. said backing plate holder being received within said backing plate holder receiving cavity in a tight fit whereby said backing plate is inherently centered by said holder relative to said axis of rotation.