Abstract: A cam grinding machine is provided wherein a wheel head is fed toward a rocking table carrying a work spindle so as to grind a cam roughly in a first step and finely in a second step successive thereto, and a speed-switchable motor is operated in such a way as to drive the work spindle and the rocking table at a fast speed in the first step and at a slow speed in the second step. The grinding machine is further provided with a motor control circuit which is arranged to switch the motor from the fast speed to the slow speed, with a delay of time that is required for the cam to rotate at least one revolution after the switching of the grinding step from the first step to the second one, so that an excessive infeed caused by the spring-back action of the cam can be reduced.

Abstract: In a grinding machine, a rest apparatus is advanced to move a workpiece toward a grinding wheel being in a stationary condition after a preliminary grinding operation. After a predetermined amount of advancement of the rest apparatus, the grinding wheel is again advanced to grind the workpiece while the rest apparatus is stationary until the workpiece deviates from engagement with the rest apparatus, whereby after a final grinding operation, the workpiece is ground at the true center thereof so as to be in true roundness and with good concentricity.