Special Welding Methods; Spot Welding - Craftsman 196.205080 Manual De Usuario

NOTE: WHEN USING SELF-SHIELDING
FLUX-CORE WIRE it is very important to
thoroughly chip and brush the slag off each
completed weld bead before making another
pass or the next pass will be of poor quality.
Figure 19. Butt Joints
Fillet Weld Joints. Most fillet weld joints, on
metals of moderate to heavy thickness, will
require multiple pass welds to produce a
strong joint. The illustrations in Figure 20
show the sequence of laying multiple pass
beads into a T fillet joint and a lap fillet joint.
Figure 20. Fillet Weld Joints

SPECIAL WELDING METHODS

SPOT WELDING

The purpose of a spot weld is to join pieces
of metal together with a spot of weld instead
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of a continuous weld bead. There are three
methods of spot welding: Burn-Through,
Punch and Fill, and Lap (see Figure 21).
Each has advantages and disadvantages
depending on the specific application as well
as personal preference.
Figure 21. Spot Welding
1. The BURN-THROUGH METHOD welds
two overlapped pieces of metal together
by burning through the top piece and into
the bottom piece.
With the burn-through method, larger wire
diameters tend to work better than smaller
diameters because they have greater cur-
rent carrying capabilities allowing the arc
to burn through very quickly while leaving
a minimal amount of filler metal build up.
Wire diameters that tend to work best,
with the burn-through method, are 0.030
inch diameter solid wire or 0.035 inch
self-shielding flux-core wire.
Do not use 0.024 inch diameter solid or
0.030 inch self-shielding flux-core wires
when using the burn-through method
unless the metal is VERY thin or
excessive filler metal build-up and minimal
penetration is acceptable.
Always select the HIGH heat setting with
the burn-through method and tune in the
wire speed prior to making a spot weld.
2. The PUNCH AND FILL METHOD
produces a weld with the most finished
appearance of the three spot weld
methods. In this method, the arc is direct-
ed through a hole punched or drilled into
the top piece of metal so that it penetrates
into the bottom piece. The puddle is
allowed to fill up the hole leaving a spot
weld that is smooth and flush with the sur-
face of the top piece.