The Haynes Welding Manual - VolksPage.Net

5.52 Instead of a straight butt-weld, panels of thin material are
often joined with spot welds, in which the top panel is punched with
small holes. You MIG-weld around the hole, joining the top panel to
the bottom.
gun. If you are welding thicker materials, or two edges that have irregular
gaps, you can weave the arc back and forth from side to side as
you travel, bridging the distance between the two edges.
Sometimes a start-and-stop technique works well for bridging gaps or filling
holes. You watch the arc and weave from one side to the other, then pause (let
go of the trigger) for a second with the torch in the same spot, allowing the puddle
to solidify, then pull the trigger again, building a new puddle onto the last one.
To fill a hole, just keep making tack-welds around the edge of the hole until you
have made it smaller (see illustration). Let the metal cool, then add an inner row
of tacks inside the first "ring" until you close up the hole with filler metal. This is
often done in filling sheet-metal holes in body work, but any hole larger than a
dime should be filled by welding in a circle of new metal of the same thickness.
The beauty of the MIG process is that the torch is a one-hand operation,
which allows you to use your other hand to steady your primary hand and draw a
smooth bead. Also the torch stays the same distance from the weld at all times,
unlike arc welding where the rod is always getting shorter.
MIG welding doesn't require stopping to change electrodes
either, so you can concentrate nicely on what you are doing.
The one-handedness of MIG welding tempts some
weldors to operate the torch with one hand while they actually
hold something on the work with their other hand. This
is OK for tack-welding, where you have a body panel you
need to hold in alignment while you tack, but better seams
are made when you hold the torch with both hands. Some
users get used to the lower brightness and spatter of the
MIG process, and are tempted to tack parts together without
using a helmet. Body men in particular are prone to
hold two panels in alignment, put the torch where it needs
to be, close their eyes and make a tack weld for a second.
Although MIG welding does produce less intense light and
spatter than arc welding, you are still subject to both radiation
burns and some spatter. Don't ever take a chance with
your eyesight. One blob of spatter onto your bare eyelid
could be really dangerous! A much better procedure (and
the only one we recommend) would be to use some clamps
or other devices (see the Safety and Shop Equipment chap-
MIG welding
5.53 Door-handle and lock holes have been filled in
on this street rod door, using small circles of sheet
metal the same thickness as the original metal. In
order to avoid warping, the circles were filled by
tacking the filler pieces in a few places, waiting for
the part to cool off, then adding a few more tacks,
until the whole circle was made of tack welds.
5.54 When welding a corner joint such as a T-section, angle
the gun at about a 45-degree angle to aim equal heat and filler
on both pieces.
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