Quality engineering methods were applied to analyze power consumption as measured by a PZ 4000 power analyzer during milling of RC 55 hardened steel to improve the milling accuracy and find the optimum machining conditions. The results led to high speed milling of this difficult-to-machine material. Application of the quality engineering methods proved useful in providing an understanding of the optimum machining conditiens, which were, for RC 55: no tool runout, down-cut, distance x=20mm from workpiece to air nozzle, cutting speed V=200m/min, depth of cut t=0.9mm, feed rate f=0.25mm/tooth, pick feed fp=1.0mm, HIT tool type. Machining characteristics were improved, and the optimum machining conditions turned out to be similar to empirical precision machining conditions.
