Sonex Reforming Aluminum Extrusions - Manual

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Builder's Guide Reforming Aluminum Extrusions
Some airframe parts require that the 90-degree aluminum
extrusion from which they are made be reformed to a greater,
or lesser bend angle. This is easily accomplished with com-
mon tools.
Accuracy
Angles are often noted very precisely on the plans (e.g. 93.7
degrees). However, there is NO NEED for an individual
builder to be nearly that precise. Often being with a degree or
two is more than enough.
Reducing the Bend Angle (Less than 90 O )
Extrusion angles are easily reduced using one of two methods:
Squeezing in a Vise: With this method the part is clamped
in a vise and squeezed to a reduced angle. When using this
method you must account for springback and squeeze the part
beyond the desired angle, as it will open up once the vise jaws
are opened.
Measuring the Angle
Angles can be measured a number of ways - an adjustable
protractor, an angle finder, lines drawn on your workbench.
Perhaps the easiest and most useful is to make a template from
a piece of non-corrugated cardboard.
After reforming an extrusion you'll want to check the new
angle in a few spots, to make sure the extrusion has been
uniformly reworked.
A file folder has been turned into a template to measure an
angle - in this example 86
O .
After the extrusions are reformed they will appear, in cross
section, as seen in the photos. Note that often only one leg is
reformed. This is normal. The angle will never bend perfectly
at the apex (corner), and there will be a small gap near the
apex.
Striking with a Mallet: Clamp one leg in a vise and strike the
other with a rubber mallet. The angle is progressively formed
by walking the mallet across the length of the angle.
This extrusion's angle is being reduced by being squeezed in a
vise. Pad the vise jaws to reduce marring of the part.
This extrusion's angle is being reduced by striking the un-
clamped leg with a rubber mallet. Pad the vise jaws to reduce
marring clamped leg.