OK, here it goes.....
The technique of forming metal is not new, but to the hobbyist it is all
about forming patch panels not re-contouring the existing metal. The
foundation for this technique is tooling.
The first thing that needs to be done is to determine where you want to have
the access. Just where on the outside isn't enough, the hose or tube routing
needs to be clear of all obstructions. Next you must find the donor gas door
with its working hinge mechanisms intact, shape is important but contour is
of primary importance. The donor door must fit within the contours of your
vehicle. When obtaining the door it is easiest for you to get the
surrounding metal so you can use it as your pattern for the tools you will
be making. The tooling consists of two wood "donuts". One for the inner
contour and on for the outer contour. Both tools should be a minimum of 1.5
inches wide and .63 inches thick. You can use plywood as tooling stock, but
I use hardwood (because I may use the tool again on another car or truck)
The rear face of the outer tool will be cut and contoured to fit flush
against the outer surface of your fender. The center will be cut out to be
.13 to .25 oversized from the required pattern for the door opening thus
making it into a ring or donut.
The front face of the inner tool must be cut and contoured to fit flush
against the inner surface of your fender, or door or whatever. It will also
be cut to the shape of the door opening including the radius (for the metal
to fold into) thus making it into a ring or donut.
It sounds simple enough, but you need to have the tool fit up exactly flush
against the body. They act as localized stiffening for the panels while you
rework the contour of the metal. Because they are clamped if they are off
the reworked metal will pull the rest of the panel into its shape, causing a
localized ripple. This is fixable as with any metal finishing but avoidable
if you mind your tooling.
Next is to determine the amount of metal that will form the radii and the
flange for the door opening. This is where the piece of quarter panel from
the donor car comes in. It can be used to determine the "flat pattern" of
the hole opening or how much metal you need to have before the flange is
formed. Measure from the top (outer) surface around the radii and to the end
of the hole (side wall) in various places around the opening. This is how
you determine the offset from the finished opening to where the required
metal ends ( this will be what you cut out of the fender). Trace the
finished opening onto your fender. Trace the offset pattern onto the fender
and fill the center of the offset pattern with hash marks.
OK, here's where it gets fun... cut out the hashed in area on your fender.
Position the inner and outer tools behind and in front of the hole. Use
C-clamps to lock the tooling together being careful to align them to the
contour and to the hole. Using a body hammer form the offset metal into the
shape of the opening, reposition the C-clamps accordingly to gain access to
the metal but make sure the tools stay firmly in place. As a note the
corners radii's are the most difficult to form as the metal is bending in
two different planes at the same time. If your door is square or rectangular
with corner radii's start at one leg and work your way around the whole
hole. It is best to do this with any pattern.
I hope this is a good start, you should always attempt new things on a
practice part first before attempting on your rare or expensive part. You
can form replacement parts this way if you require repetitive parts. You can
use the formed tools on a flat sheet of metal as well.
Jon C. Peters
51 GMC (with a LOT of and formed panels)
51 Chevy coupe
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
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