Lapping machine

摘要

This invention relates to a lapping machine having a platen (1) which is stable to the temperature change, and provide a lapping machine which possesses a platen (1) made of cast iron alloy containing 1.0 SIMILAR 4.0 wt% of carbon, smaller than 38 wt% of summed weight of nickel and cobalt, smaller than 2.0 wt% of silicon, smaller than 2.0 wt% of manganese, smaller than 0.1 wt% of sulfur, smaller than 0.15 wt% of phosphorus, smaller than 0.1 wt% of magnesium and balancing weight of iron. Spherical graphite grains smaller than 50 mu m diameter are dispersed in said cast iron alloy by smaller than 150pieces/mm<2> density, and the thermal expanding co-efficiency of said cast iron alloy is smaller than 5 x 10<-6>/ DEG C.