Spot Welding Instructions - Matco Tools MP200DVILCD Owner's Manual

e. Spot Welding
There are three methods of spot welding: Burn-Through, Punch and Fill, and Lap. Each has
advantages and disadvantages depending on the specific application as well as personal
preference.
i. 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. Wire diameters that tend to work best, with the burn-through method
are 0.035 inch self-shielding flux-core wire. Do not use 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.
ii. The PUNCH AND FILL METHOD produces a weld with the most finished
appearance of the three spot weld methods. In this method, a hole is punched or
drilled into the top piece of metal and the arc is directed through the hole to
penetrate into the bottom piece. The puddle is allowed to fill up the hole leaving
a spot weld that is smooth and flush with the surface of the top piece. Select the
wire diameter, heat setting, and tune in the wire speed as if you were welding
the same thickness material with a continuous bead.
iii. The LAP SPOT METHOD directs the welding arc to penetrate the bottom and
top pieces, at the same time, right along each side of the lap joint seam. Select
the wire diameter, heat setting, and tune in the wire speed as if you were
welding the same thickness material with a continuous bead.

5. SPOT WELDING INSTRUCTIONS

a. Select the wire diameter and heat setting recommended above for the method of spot
welding you intend to use.
b. Tune in the wire speed as if you were going to make a continuous weld.
c. Hold the nozzle piece completely perpendicular to and about 1/4 inch off the work piece.
d. Pull the trigger on the torch and release it when it appears that the desired penetration has
been achieved.
e. Make practice spot welds on scrap metal, varying the length of time you hold the trigger,
until a desired spot weld is made.
f. Make spot welds on the actual work piece at desired locations.
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