bend 24 gauge sheet metal at that setting, the sheet will
slip and the bend will be formed in the wrong position.
When you try to bend 18 gauge sheet metal when the
machine is set for 24 gauge sheet metal, you can break
the clamping bar handle. The pressure to lock the
clamping bar should NEVER be too strong. With a little
practice you will be able to gauge the pressure correctly.
2. Adjust the upper jaw horizontally to the correct
position for the thickness of the metal and for the radius
of the bend to be made.
If the upper jaw is adjusted to the exact
thickness of the metal, the bend will be sharp
or it will have practically no bend radius. If it
is set for more than the thickness of the metal,
the bend will have a larger radius; if the jaw is
set for less than the thickness of the metal, the
jaws of the machine may be sprung out of
alignment and the edges of the jaws may be
After these two adjustments have been made, the
machine is operated as follows:
1. Scribe a line on the surface of the sheet metal to
show where the bend will be.
2. Raise the upper jaw with the clamping handle
and insert the sheet in the brake, bringing the scribed
line into position even with the front edge of the upper
3. Clamp the sheet in position. Ensure that the
scribed line is even with the front edge of the upper jaw.
The locking motion will occasionally shift the
4. Once you are satisfied that the metal is clamped
correctly, the next step is to lift the bending leaf to the
required angle to form the bend. If you are bending soft
and/or ductile metal, such as copper, the bend will be
formed to the exact angle you raised the bending leaf.
If you are bending metal that has any spring to it, you
will have to raise the bending leaf a few degrees more
to compensate for the spring in the metal. The exact
amount of spring that you will have to allow for depends
on the type of metal you are working with.
5. Release the clamping handle and remove the
sheet from the brake.
The brake is equipped with a stop gauge,
consisting of a rod, a yoke, and a setscrew. You use
this to stop the bending leaf at a required angle. This
feature is useful when you have to fabricate a large
number of pieces with the same angle. After you have
made your first bend to the required angle, set the stop
gauge so that the bending leaf will not go beyond the
required angle. You can now fabricate as many bends
as you need.
The cornice brake is extremely useful for making
single hems, double hems, lock seams, and various
It is impossible to bend all four sides of a box on a
conventional brake. The FINGER BRAKE, sometimes
referred to as a BOX AND PAN BRAKE (fig. 2-37), has
been designed to handle this exact situation . The upper
jaw is made up of a number of blocks, referred to as
fingers. They are various widths and can easily be
positioned or removed to allow all four sides of a box to
be bent. Other than this feature, it is operated in the same
manner as a cornice brake.
ROLL FORMING MACHINE. W h en
cylinders and conical shapes are being formed, no
sharp bends are obviously required; instead, a gradual
curve has to be formed in the metal until the ends meet.
Roll forming machines have been invented to
accomplish this task. The simplest method of forming
these shapes is on the SLIP ROLL FORMING
MACHINE (fig. 2-38). Three rolls do the forming
(fig. 2-39). The two front rolls are the feed rolls and
can be adjusted to accommodate various thicknesses
of metal. The rear roll, also adjustable, gives the
section the desired curve. The top roll pivots up to
permit the cylinder to be removed without danger of
distortion. Grooves are machined in the two bottom
Figure 2-37.Finger brake.