Machine for parallelly lapping opposite surfaces of a workpiece

Claim 1

An improvement in a machine for ultra precision parallel lapping of the opposite surfaces of a workpiece by a rotatable lapping plate, comprising: a. a base ring having a top wall and positioned on and rotatable by the lapping plate, b. an elongated longitudinally slit sleeve connected to and extending from said top wall, c. an elongated ram embraced by said sleeve and having longitudinal movement with respect thereto, d. a pressure plate arranged within said ring and connected to said ram, e. said ram having an elongated longitudinally extending keyway formed in one side thereof, f. a key carried by said sleeve and engaging said keyway to provide rotatable connection between said sleeve and said ram while permitting longitudinal movement of the ram relative to the sleeve, g. means for contracting and expanding said sleeve to vary the degree of frictional engagement between the sleeve and the ram, h. said means comprising two sets of bolts, the ends of one of said bolts engaging the wall surfaces of the sleeve defined by the slit and adapted to expand said sleeve when rotated in a clockwise direction, the other set of bolts threaded into openings formed in the sleeve for contracting the sleeve when said bolts are rotated in a clockwise direction.