過共晶Al-Si合金の穴あけ加工におけるバニシングについて

抄録

Increase in torque and creaky noise often encountered in drilling hyereutectic Al-Si alloys were studied in various drilling conditions. The torque increase and creaky noise are caused by burnishing of a drill margin and a hole wall. Cyclic fluctuation of torque exactly corresponds to the profile of a hole with poor roundness. The burnishing easily occurs at a low built-up edge and under considerable drill wear. A built-up edge is formed in drilling on the margin face resulting in enlarging the effective drill diameter and preventing the burnishing. Recession of a cutting edge by wear accelerates burnishing because of an increase in margin contact with a hole wall. Hypereutectic Al-Si alloys particularly T6 treated permit a low built-up edge and considerable drill wear.