TECH INSTALL FABRICATE UPGRADE
with an English wheel earlier in the
day. I gave this panel a medium-
crown curvature, similar to fenders
and hoods on many early trucks.
I clamped this panel between two
workbenches, giving me clear
access to the top and bottom of the
panel. Having good accessibility is
very important for doing high-
quality metalwork.
To keep things moving quickly,
I made a relatively small patch
panel, but the same principles apply
to patches of any size. To mark
the opening, I scribed around the
edge of a roll of masking tape. This
produced a fairly accurate circle
about 4 inches in diameter. Patches
with square corners distort more
when welded, so if it’s feasible to
round the corners of your patches,
it may be worth the extra effort.
I used a step drill to make a ½-
inch hole in the center of the circle,
allowing me to insert the tips of my
aircraft shears, then I made a cut
that spiraled out toward the scribed
line. This roughing cut removed the
bulk of the waste, so on the final
cut I was removing a ribbon of
metal about ¼-inch wide.
Next, I domed a piece of metal
for the patch by hammering on-
dolly. This piece was placed under
the panel and pressed up so it made
contact all around the opening,
and I scribed around the perimeter,
marking the patch for trimming.
Before releasing my grip, I used
a felt-tipped marker to make a
“witness” line on the patch and
the base metal. The hand-trimmed
opening is close to being round,
but slight irregularities mean the
patch will only fit properly in one
orientation.
Now I can check the fit of the03 Here I’m holding the patch under the
panel and scribing it for trimming.
04 Since the round hole was hand-cut,
it’s not perfect, so it’s important to put a
“witness mark” on both parts, so you know
how they fit together.05 I prefer using a butt-weld for patch
panels, and the fit is so good that the
patch holds itself into place. I’m using a TIG
welder for the tacking.