(5) When using a chisel for chipping. always wear goggles to protect your
eyes. If other men are working close by, see that they are protected from flying
chips by erecting a screen or shield to contain the chips. Remember that the time
to take these precautions is before you start the job.
f. Punches.
(1) A hand punch is a tool that is held in the hand and struck on one end
with a hammer. There are many kinds of punches designed to do a variety of jobs
and most are made of tool steel. The part held in the hand is usually octagonal
shaped or it may be knurled. This prevents the tool from slipping around in the
hand. The other end is shaped to do a particular job. Figure 40 shows some of the
most common used metal punches.
Figure 40.
Commonly used metal punches.
(2) Drift punches, sometimes called "starting punches", have a long taper
from the tip to the body. They are made that way to withstand the shock of heavy
blows. They may be used for knocking out rivets after the heads have been chiseled
off, or for freeing pins which are "frozen" in their holes. After a pin has been
loosened or partially driven out, the drift punch may be too large to finish the
job. The followup tool to use is the pin punch, for it is designed to follow
through the hole without jamming. Always use the largest drift or pin punch that
will fit the hole. These punches usually come in sets of three to five assorted
sizes and will have flat points, never edged or rounded. To remove a bolt or pin
that is extremely tight, start with a drift punch that has a point diameter
slightly smaller than the diameter of the object you are removing. As soon as it
loosens, finish driving it out with a pin punch. Never use a pin punch for
starting a pin, because it has a slim shank and a hard blow may cause it to bend or
break.
(3) Another punch you will use a lot is the center punch. As the name
implies, it is used for marking the center of a hole to be drilled. If you try to
drill a hole without first punching the center, the drill will "wander" or "walk
away" from the desired center. Another use of the center punch is to make
corresponding marks on two pieces of an assembly to permit reassembly in their
original positions. The point of a center punch is accurately ground central with
the shank, usually at a 60 angle, and is difficult to regrind by hand with any
degree of accuracy. It is, therefore, advisable to take care of a center punch and
not to use it on extremely hard materials.
(4) Other punches have been designed for special uses. One of these is the
soft-faced drift. It is made of brass or fiber and is used for such jobs as
removing shafts, bearings, and wrist pins from engines. It is generally heavy
enough to resist damage to itself, but soft enough not to injure the finished
surface on the part that is being driven.
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