Electric and hand drills
(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 25).
b. Care and Use of Boring Tools. To cut a clean, splinterfree
hole, the cutting parts must be kept sharp. The spur must be kept
sharp so that it will pull the bit into the wood. The lip must be
kept sharp to prevent tearing of the material being bored. Because
these are all sharp edges, the lip should be protected from damage
through contact with other tools. Bits should be stored a special
case, or the point wrapped with a rag to protect the cutting edges.