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Bending Sheet Metal
This machine can make up to 90° bends in sheet
metal. Refer to the Machine Data Sheet on Page
4 to determine the workpiece capacities of your
particular model. When you use the hand crank,
the brake fingers force the workpiece into the
groove of the finger receiver to make the desired
bend (see Figures 28–29).
Workpiece
Figure 28. Side profile of brake fingers and
receiver making 90° bend in workpiece.
Finger
Receiver
Figure 29. Identifying brake fingers and receiver
on machine (G4011Z shown).
T26472Z/G4011Z/T26751Z (Mfd. Since 02/14)
Brake
Finger
Finger
Receiver
When metal is bent, the outside overall dimension
increases from its original length—this amount is
called the bend allowance. A typical bend allow-
ance for a 90° bend in a 22-gauge mild steel
workpiece is approximately 0.050". That means
you need to start with a workpiece that is approxi-
mately 0.050" shorter than the desired outside
length of the finished workpiece, as illustrated in
Figure 30.
Desired Workpiece Length After Bend = 2"
2" - 0.050" = 1.950"
Length of Initial Blank
0.050" Bend Allowance
To Be Subtracted from 2"
Finished Workpiece
B
Figure 30. Example of accounting for bend
allowance.
Calculating the bend allowance requires factor-
ing in many variables, such as metal thickness,
type of material, radius of the bend, etc. Detailed
information for calculating the bend allowance can
be found in metalworking handbooks and on the
internet.
One way to calculate bend allowance for any
workpiece is to measure a piece of scrap material
that is the same material as the workpiece, create
the same bend intended for the workpiece, then
measure it again. The difference between the
two measurements is the bend allowance, which
you subtract from the dimension of the workpiece
blank before the bend.
A
A + B = 2"
-21-
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