USE/CARE OF HANDTOOLS & MEASURING TOOLS - OD1621 - LESSON 2/TASK 2
(4) Restoring Temper.
If the point or the flat end of a punch is
ground beyond the hardened section, or if the mushroomed head was reshaped
or if the punch was overheated in grinding, the punch must be hardened and
tempered.
7.
Shears
a. Purpose.
Shears are used for cutting sheet metal and steel of
various thicknesses and shapes.
b. Types of Shears. Shears are made in a variety of shapes and sizes
and are used according to their design and capacity.
Hand shears (figure
114 on the following page) are used for light work and are made with
straight or curved cutting blades.
Straight bladed shears are used for
cutting straight lines and to cut curves in easily accessible locations.
Shears with curved blades, such as the hawk bill and the curved blade hand
shears, are made especially for cutting short straight lines or curves.
They are also used for cutting out small intricate designs in locations
where it is advantageous to keep the handles and handle operating hand away
from the metal stock.
Shears are made for right-hand operators so the
cutline is always in full view for accurate cutting when the shears are held
in the right hand.
c. Use of Shears.
(1) Straight Cuts. To make straight cuts, place the sheet metal on a
bench with the marked guideline over the edge of the bench; hold the sheet
down with one hand. Hold the shears so that the flat sides of the blades
are at right angles to the surface of the work. If the blades are not at
right angles to the surface of the work, the edges of the cut will be
slightly bent and burred.
The bench edge will also act as a guide when
cutting with the shears. The shears will force the scrap metal down so that
it does not interfere with cutting. Any of the hand shears may be used for
straight cuts.
When notches are too narrow to be cut out with a pair of
shears, make the side cuts with the shears and cut the base of the notch
with a machinist's cold chisel.
148
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