(1) Auger Bit. Auger bits come in sizes from 1/4 inch to 1 inch. The number on the tang shows the size of the bit in 1/16-inch increments. For example, in Figure 2-1 the number 6 means that it is 6/16 (or 3/8) inch. The marked part of the bit is used to start the hole. The spur is made like a screw, which pulls the bit into the wood as you turn the bit. The parts marked lip and nib are the cutting parts. The twist portion removes the shavings from the hole. The shank ends in a tang, which fits into the brace.

(2) Expansion Auger Bit. An expansion bit (Figure 2-2) is used to bore a hole larger than 1 inch, such as for a door lock. Notice that the cutting bit has a scale for adjusting the size of the hole needed. The screw shown is used to lock the cutting blade into position. The screw must be tightened to keep the blade from moving and changing the size of the hole. This bit also has a tang to fit into the hand brace.

(3) Twist Drill. A twist drill is used to make holes in wood, metal, fiber, plastic, and other materials. Carpenters often drill holes in metal to which some type of wood or fiber will be bolted. This requires the use of a special type of twist drill (Figure 2-3). Twist drill bits are driven by electric or hand drills (Figure 2-4).

(4) Countersink Bit. A countersink bit is used to increase the diameter of the top of a drilled hole to receive the head of a screw (Figure 2-5).