Abstract: During grinding of successive workparts with a superabrasive wheel in a rough grind stage at a high wheel infeed rate and a finish grind stage at a relatively low infeed rate with spark-out stages after each of the rough and finish grind stages, the duration of the spark-out stage after rough grinding is made dependent on the condition of the grinding wheel and corresponds to the time needed for removing workpart material for the reduction of the grinding wheel motor power from the high rough grind level to the lower finish grind level. The duration of the spark-out stage will therefore be variable from one workpart to the next as the condition of the wheel changes. In addition, the interval of wheel retruing or dressing (i.e. number of workparts ground between wheel retruing) is variable as determined by the condition of the wheel. In particular, when the rough spark-out stage for a workpart is completed in a time shorter than a preselected minimum time indicative of a wheel that is in need of retruing.

Abstract: The grinding wheel infeed control method provides a constant infeed rate calculated on the average electrical power consumed by the wheel drive motor in rough grinding an immediately preceding workpart. Each subsequent workpart is rough ground at a constant infeed rate established from the wheel drive motor power consumption of the immediately preceding workpart until the grinding wheel is in need of re-trueing or re-dressing. The first workpart ground after wheel re-trueing or re-dressing is ground at a rough (high) infeed rate which is continuously varied by the machine control computer so as to maintain the electrical power consumed by the grinding wheel drive motor substantially constant at a preset level and from which the constant infeed rate for the second workpart is determined.

Abstract: In the internal grinding of a cylindrical bore having an oil or similar groove which adversely affects the bore roundness achievable, one or more streams of liquid coolant are directed over the grinding wheel during rough grinding at a high wheel feed rate and only a mist of liquid coolant droplets suspended in a compressed air stream is directed over the wheel once the high wheel feed rate has been reduced to the lower wheel feed rate associated with finish grinding. Means are provided for terminating the liquid coolant streams at the time the wheel feed rate is changed or after a short delay period thereafter to establish equilibrium finish grind conditions. Preferably, the change from one or more liquid coolant streams to the coolant mist is made in response to a detected decrease in wheel spindle motor power.