4. General appearance. The dimple should be
checked with the fastener that is to be used, making
sure it meets the flushness requirement. This is
important because the wrong type or size of dies are
sometimes used by mistake.
Squaring Shears
Squaring shears are used for cutting and squaring
sheet metal. See figure 13-17. They may be foot
operated or power operated. Squaring shears consist
of a stationary blade attached to a bed and a movable
blade attached to a crosshead. To make a cut, place
the work in the desired position on the bed of the
machine. Then use a downward stroke to move the
blade. Foot-powered squaring shears are equipped
with a spring that raises the blade when foot pressure
is removed from the treadle. A scale graduated in
fractions of an inch is scribed on the bed. Two side
guides, consisting of thick steel bars, are fixed to the
bed, one on the left and one on the right. Each is
placed so that its inboard edge creates a right angle
with the cutting edge of the bed. These bars are used
to align the metal when square corners are desired.
When cuts other than right angles are to be made
across the width of a piece of metal, the beginning and
ending points of the cut must be determined and
marked in advance. Then the work is carefully placed
into position on the bed with the beginning and ending
marks on the cutting edge of the bed.
Figure 13-17.—Squaring shears.
A hold-down mechanism is built into the front of
the movable cutting edge in the crosshead. Its
purpose is to clamp the work firmly in place while the
cut is being made. This action is quickly and easily
accomplished.
The handle is rotated toward the
operator and the hold-down lowers into place. A firm
downward pressure on the handle at this time should
rotate the mechanism overcenter on its eccentric cam
and lock the hold-down in place. You should reverse
the action to release the work.
Three distinctly different operations—cutting to a
line, squaring, and multiple cutting to a specific
size—may be accomplished on the squaring shears.
When you are cutting to a line, place the beginning
and ending marks on the cutting edge and make the
cut. Squaring requires a sequence of several steps.
First, square one end of the sheet with one side. Then
square the remaining edges, holding one squared end
of the sheet against the side guide and making the cut,
one edge at a time, until all edges have been squared.
When several pieces are to be cut to the same
dimensions, you should use the adjustable stop gauge.
This stop is located behind the bed cutting edges of
the blade and bed. The supporting rods for the stop
gauge are graduated in inches and fractions of an inch.
The gauge bar is rigged so that it may be set at any
point on the rods. With the gauge set at the desired
distance from the cutting blade, push each piece to be
cut against the stop. This procedure will allow you to
cut all pieces to the same dimensions without
measuring and marking each one separately.
NOTE: After you cut the first piece in a
series, measure it to make sure that the stop is
accurately set.
Throatless Shears
Throatless shears are constructed so sheets of any
length may be cut and the metal turned in any
direction during the cutting operation. See
figure 13-18. Irregular lines can be followed or
notches made without distorting the metal. Throatless
shears are an adaptation of heavy handshears or snips
in which the handles are removed, one blade secured
to a base, and a long lever attached to the tip of the
movable blade. The heavy duty throatless shears are
capable of cutting stainless steel up to 0.083 of an
inch thick.
13-12
