3. Start the machine and cycle it through one
several tons of pressure to prevent movement
complete revolution to check the machine for proper
of the plate during the shearing action.
operation and binding.
The back gauge (not shown) is at the back of
4. Stop the machine and place the plate flat on the
the machine and provides a stop for the exact
bed and snug against the back gauge. Ensure the metal
measurements for shearing more than one
is under a holddown.
piece of plate. The back gauge is usually set
5. Start the machine and engage the holddowns
from an adjustment wheel on the front of the
manually, if desired, or check the holddown lever to
machine.
ensure that it is in the proper mode. For inexperienced
operators, the shear lever should always be in the ONCE
The bed is the flat part of the shear that provides
position.
a surface and support for the metal to be
6. Depress the trip lever and shear the plate. If the
sheared.
dogs were not previously set, they will automatically
engage when the trip lever is depressed.
The flywheel is on the left side of the machine.
KNIFE SETTING AND CLEARANCE.--After
It is part of the pulley system that sets the
repeated use of the shear, the knives will begin to wear.
machine in motion. Some machines use a
You will begin to notice that the sheared plate will have
hydraulic system and cylinder in place of the
rough edges and burrs left on the edge. A worn blade
flywheel/pulley system.
will decrease machine efficiency and will require
additional work to remove the burrs from the edge. You
A set of upper and lower cutting knives provide
should also inspect the knives periodically for
the shearing action.
indentations, cracks, dullness, and other signs of wear
that could cause inefficient operation.
The control panel is a station from which the
Setting The Knives.--If the knives show signs of
shear is operated. The control panel has a
wear but do not need replacement, you may simply
stop/start button, a control lever for the dogs so
rotate the knives to a new cutting edge. Each knife has
that they can engage manually, and a control
four cutting edges that enable the knives to be rotated
lever for the shearing action. The control lever
until each edge has been used. When rotating the
for the shearing action usually has three
knives, rotate the upper and lower blades together so
positions: OFF, JOG, and ONCE. In the JOG
that you have two new cutting edges exposed. The
position, the machine will cut repeatedly as
following is a general description of how to rotate or
long as the trip lever is depressed. In the ONCE
replace the knives:
position, the shear will only make one cutting
NOTE: Always refer to the manufacturer's
revolution when the trip lever is depressed.
technical manual for the particular machine installed in
your shop for the correct procedure for blade setting.
The final item is the trip device that sets the
machine in motion. This lever is usually foot
Block the ram in the up position while
operated and is of the foot pedal type or the bar
removing the upper knife.
type (which runs the length of the machine).
OPERATION OF THE DROP SHEAR.--
Remove the knives from the scats. The knives
Operation of the drop shear is a relatively simple
will have shims installed between the knife and
operation provided you follow all manufacturers'
the blade, so ensure that you save the shims and
directions and safety precautions. The following is a
m a r k the location of each shim for
list of procedures to follow when setting and loading the
reinstallation.
machine for operation.
1. Determine that the plate to be sheared does not
Rotate or install new knives, as required.
exceed the capacity of the machine.
2. Adjust the back gauge for the proper cutoff
Tighten the knife by holding it firmly against
length.
the seat. Pry the upper knife with a wooden
13-21
