A slitting mechanism has one or more slitting shafts between rotating brackets. The metal line structure of the optical scanner includes: a glass substrate having a metal line region etched to a predetermined depth; a metal line formed in the metal line region; a diffusion barrier layer that is formed on the glass substrate and covers the metal line; and an optical scanner structure combined with the glass substrate. The push portion is exposed outward to be pushed and has a plating layer 12 or 12\u2032 formed thereon, and the switch contact selectively operates a tact switch 4 or 4\u2032. Both ends of each of relay coils C provided to the relays 22a to 22c are connected to an ECU 5, and the ECU 5 controls a current flowing through the relay coils C and thereby controls the turning on and off of the relays 22a to 22c. The drill bit may also comprise a junk slot for return flow of the drilling fluid and solid material impactors. In another preferred embodiment the hollow lightweight aluminum handle has a straight shape.