8. Continue turning the sheet end over end and
Bending on a Bar Folder
passing it through the rolls, each time adjusting the rear
The bar folder may be used to bend and fold metal
roll for a new radius, until a cylindrical shape has been
in a number of different shapes, as illustrated in figure
formed.
4-37. This machine has two adjustments: one for
9. Remove the cylinder from the machine. The
regulating the width of the fold and the other to provide
top front roll has a quick-releasing device on one end.
sharp or rounded bends. To operate the bar folder,
This allows the released end of the roll to be raised and
adjust the thumbscrew to the specified width of the
the newly formed cylinder slipped off just as you would
fold. Then turn the adjusting knob on the back of the
slip a ring from your finger.
machine for the desired sharpness of the bend. Insert
Conical shapes can be formed by setting the back
the metal under the folding blade until it rests against
roll at an angle before running the sheet through it, or
the stops. Hold the metal firmly in place with one hand,
grasp the handle with the other, and pull forward until
the desired fold is made.
FORMING SHEET METAL
A sheet metal object made on a brake will have
corners (bends) and sides (flanges). On a forming
machine, it is possible to make an object without sides.
For example, you can make a circular object such as a
funnel. The forming machines used in the Navy are
usually located at aircraft intermediate maintenance
departments (AIMDs). The two most common
machines are the slip roll and the rotary.
Slip-Roll Forming
Sheet metal can be formed into cylindrical or
conical shapes through the use of the slip-roll forming
machine. Prior to using this machine, you should
consult the manufacturers manual of operation.
To form a cylinder in the machine, you should use
the following procedures and refer to figure 4-38:
1. Adjust the front rolls so they will grip the sheet
properly.
2. Adjust the rear roll to a height that is less than
enough to form the desired radius of the cylinder.
3. Ensure that all three rolls are parallel. (The
same space exists between any two rollers at each end
of the rollers.)
4. Start the sheet into the space between the two
front rolls. As soon as the front rolls have gripped the
sheet, raise the free end of the sheet slightly.
5. Pass the entire sheet through the rolls. This
forms part of the curve required for the cylinder.
6. Set the rear roll higher to form a shorter radius.
7. Turn the partially formed sheet end over end,
and again pass it through the rolls.
Figure 4-38.--Forming a cylinder.
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