PURPOSE: To prevent the breakdown of a drill by providing a pressure sensor, temperature sensor, etc. in the drill and operating it under optimal condition.

CONSTITUTION: A ceramic coating is applied on the surface of the boring edge of a drill 1. The pressure to be applied on the edge 11 of the drill 1 and the degree of contact are read out by a pressure sensor 2. The heat to be produced at the boring edge 12 is confirmed by a temperature measuring sensor 3. The data is connected through leads 21, 31 to an automatic controller 4 to control the boring work automatically. When applying the ceramic coating, the broken edge can be recovered easily.