The principal parts of a twist drill are the body, the
shank, and the point (fig. 1-24). The dead center of a
drill is the sharp edge at the extreme tip end of the drill.
It is formed by the intersection of the cone-shaped
surfaces of the point and should always be the exact
center of the axis of the drill. The point of the drill
should not be confused with the dead center. The point
is the entire cone-shaped surface at the end of the drill.
The lip or cutting edge of a drill is that part of the
point that actually cuts away the metal when drilling a
hole. It is ordinarily as sharp as the edge of a knife.
There is a cutting edge for each flute of the drill.
The shank is the part of the drill that fits into the
socket, spindle, or chuck of the drill press. Several
types exist (fig. 1-25).
The maintenance of twist drills and more about
how to use them on specific jobs are discussed later.
Identify the different types of metal-cutting
What are hawks-bill snips used for?
What are hacksaws used for?
What are taps and dies used for?
LEARNING OBJECTIVES: Identify the
different types of wrenches. Describe the uses
of different types of wrenches. List the safety
precautions that apply to wrenches.
A wrench is a basic tool that is used to exert a
twisting force on bolt heads, nuts, studs, and pipes. The
special wrenches designed to do certain jobs are, in
most cases, variations of the basic wrenches that are
described in this section.
The best wrenches are made of chrome vanadium
steel. Wrenches made of this material are lightweight
and almost unbreakable. This is an expensive material,
however, so the most common wrenches found in the
Navy are made of forged carbon steel or molybdenum
steel. These latter materials make good wrenches, but
they are generally built a little heavier and bulkier to
achieve the same degree of strength as chrome
Figure 1-24.Twist drill nomenclature.
Figure 1-25.Representative shanks.