TECH INSTALL FABRICATE UPGRADE
and place a tack there. The patch
seldom fits perfectly in the beginning,
so I place my tacks where I have the
best alignment. On the first go-around
I was able to make six tacks, which
were fairly evenly spaced around the
perimeter.
Once the patch was held with
several tacks, I worked the entire
perimeter of the joint with a hammer
and dolly. The patch is held solidly
at the tacks, but the metal between
the tacks may still be floppy at this
point—my goal is to prepare the
metal for the next tacks. Gaps can
be reduced, or even eliminated, by
hammering on-dolly. Then the next
tacks are made. I go through as many
rounds of tacking and hammering as
it takes until I have a good fit-up all
around the joint, with the tacks no
more than ½-inch apart.
With the last tacks in place, I
work the joint one more time with
the hammer and dolly to ensure
the fit-up is as good as I can get it.
Remember, the better the fit, the better
the weld; and the tighter the fit, the
less distortion you will get. I like to
rock a straightedge across the panel at
this stage to highlight any high or low
spots, which can be corrected with
more hammer and dolly work.
Now I’m ready for the finish
welding. I normally make welds about
1-inch long, then skip about 2 inches
for the next weld, going around
the perimeter of the patch. Welding
on sheetmetal causes it to shrink,
so I hammer on-dolly on the welds
to bring them back to the proper
contour. Then I go back and add about
1 inch to the ends of the first welds.
I alternate between welding and
hammering until the entire joint is
welded completely.
I checked the welded joint with
a straightedge at this point to get
a good reading on any high or low
spots. Deviations can be corrected
with more hammer and dolly work.
You should be able to get the panel
close enough so it only requires a tiny
amount of plastic filler at this stage, if
that’s your goal.
Next month we’ll get into
Metalfinishing—the process of getting
the smoothest finish possible, which
may allow you to do work that
requires no filler whatsoever!09 Here’s the patch, held securely with
many small tack welds.
10 I’m rocking a straightedge back and
forth across the panel to help show any
high or low spots. These are corrected with
hammer and dolly work before the finish
welding is done.11 For
the finish
welding, I
like to skip
around the
perimeter of
the patch,
making
welds about
1-inch long.
Each weld is
hammered
to relieve the
shrinking.
12 For the second round of welding, I add
about 1 inch to the ends of the first welds. 13 Here’s the patch completely welded.
14 I’m using a straightedge again to check
the contour of the panel. Note how the
welded area has pulled down. This will be
corrected with more on-dolly hammering.
15 Here’s a look at the inside of the panel
after hammering the joint. Notice how
uniform the penetration is, and how the
hammering has crushed the weld nearly
flat.64 classictrucks.com