Grinding machine

In a grinding machine having a frame, a wheelhead mounted on said frame, a wheel spindle rotatably mounted on said wheelhead, and a grinding wheel having a grinding surface secured to said spindle, a workhead adjustably mounted on said frame, said workhead comprising:

• a work spindle for holding a workpiece carried by said workhead, said work spindle being carried by bearings mounted on said workhead,
• means for mounting said work spindle for rotatable and axial movement with respect to said grinding surface whereby said workpiece can be oriented with respect to said grinding surface and brought into contact with said grinding surface,
• power means for rotating said work spindle,
• a screw element having threadably mounted thereon a nut element, said nut element and said screw element being mounted for relatively rotatable movement with respect to one another to displace said elements axially with respect to one another, said nut element having outer teeth and being rotatably mounted on said workhead and fixed against axial movement with respect to said workhead, said work spindle being coaxial with said nut element and passing through said nut element, said screw element comprising the outer surface of a first ring movable axially,
• a second ring attached to said work spindle and rotatably and axially movable therewith, said second ring being engageable by said first ring to cause axial movement of said work spindle, and
• means for rotating said screw element and said nut element with respect to one another comprising a step-by-step reversible electric motor carried by said workhead and having an output shaft means rotatable by a predetermined number of electric pulses, said output shaft means directly rotatably engaging said outer teeth of said nut element whereby rotation of said nut element by said output shaft means results in axial movement of said work spindle with respect to said workhead.