抄録
High speed drilling machines equipped with spindles supported by hydro-static air bearings and driven by air turbines are manufactured and employed in high speed micro deep drilling of holes from 0.1 mm to 0.9 mm in diameter. A special drilling machine with which relative rotational motions can be applied to both the drill and the workpiece is developed and applied in addition to the drilling machine of conventional type. The maximum rotational speed of the main spindles is 180 000 rpm. The drills are made of high speed steel and carbide. Drilling tests are carried outfor free machining stainless steel SUS 303 Se and brass. The torque and the thrust during drilling and the wear of the drills are measured. The chips, the drilled holes and the burrs are also examined after the drilling tests. It is found that the sharpness of the cutting edges of the drill has much effect upon the cutting forces and the accuracy of the drilled holes, since the drilling is performed at very high rotational speed and yet at minute feed rate. It is also found that the formation of the burrs are suppressed when the relative rotational motions are applied to the drill and the workpiece.
