Manual Brake Installation, Operation, and Maintenance Manual
HEMMING
Hemming is the most difficult operation to control accurately on a hand brake.
Hemming creates pressure loads on the machine different than those created by
regular bending, and optimum results will not be obtained using the same machine
preloading for both hemming and bending.
In factory tests, closing 24 Ga. material all the way along was done easily with no
change in the preloading settings used for bending. 22 Ga. material was open about
1/32 inch in the middle and hems in 20 Ga. had an opening in the middle of just
under 1/16 inch under like conditions.
If you must have tight hems in material heavier than 24 Ga., do all of the bending
first, adjust the machine for hemming, and close the hems in a second operation.
Hemming is traditionally done by making a maximum bend of about 135 degrees
and flattening it between beam and bed by lowering the clamping levers.
This approach may require additional preloading in order to close the hem tightly
at the center. Increase the preload by tightening the upper beam tensioning
adjusting nut (see Figure 9).
It also requires reducing clamping pressure to allow for multiple thicknesses of
material. Reduce clamping pressure by slackening the lower toggle pin adjusting
nut and tightening the upper toggle pin adjusting nut (See Figure 10).
Remove the workpiece from the machine after bending. Close the machine by
clamping the beam down on the bed with the clamping levers. Place the workpiece
on the front surface of the upper beam. Swing the apron up and close the hem by
squeezing the workpiece between the machined surface of the apron and the upper
front surface of the radius bar.
This may feel awkward at first, especially if you are accustomed to hemming in the
traditional manner, but it will get easier with practice and the end result is far
superior to the traditional way.
It may be necessary to move the upper beam 1/8" to 3/16" to the rear to allow
clearances for the hem between apron and front of beam. See
SETUP, SECTION
5
, for adjustment instructions.
HEMMING...
...THE
TRADITIONAL
METHOD
HEMMING...
...ANOTHER WAY
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