Fig. 75. Countersink Bit.

Fig. 76. Screwdriver Bit.

The countersink bit, Fig. 75, is used to enlarge the holes bored for the bodies or cores of flat-head screws, that the heads may be sunk slightly below the surface of the wood.

The screwdriver bit, Fig. 76, is used in connection with-the brace for the rapid insertion of screws. To avoid the screwdriver bit's jumping out of the groove in the head of the screw, after each half turn of the crank, move the crank backward very slightly.