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Hobart Handler 140 - different thickness metal joint and use of SEM weld thru primer

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  • Hobart Handler 140 - different thickness metal joint and use of SEM weld thru primer

    I'm pretty much a novice welder and can achieve some decent welds. However with not welding a lot I can produce some sloppy welds quickly. The other day I made a frame from 2x3 x 1/8 tubing. I capped the ends with fitted 1/8 plates. I set the Hobart for 4/40 per the chart and everything worked out perfect. So today I'm trying to weld 1/8 thick plates to something around 18-20 ga. steel. This is actually the inside rockers of a uni-body car and I'm "plating" them to weld in some custom 2x3 tubing frame. This is a junker car as I practice for the good car. So I use SEM primer (pictured) on the rocker and on the back side of the 1/8 plate. All I get is popping and carrying on and really crappy welds. I tried the 4/40 setting and the 3/35 to experiment. Would the primer cause this? I am grounded to wire wheeled steel about 6 inches away. What settings should I try on the different thickness materials? Gas is good too. I also find if I weld vertical top-down the welds are nicer. Bottom-up the look like big fat boogers.
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  • #2
    Weld through would be a more appropriate term for using higher voltages and currents than it is for low voltage low current. Weld metal does not readily bond to copper, that's why we use copper as a backer a lot. Zinc actually combusts at welding temperatures which complicates low current applications. Plus there are the binding agents, some pigment and fillers (clay) in any primer. This all makes it less than ideal, much like welding dirty metal.

    Stick welding, you could blow through it, still less than ideal. MIG at higher currents, get it it hot enough to burn the crud out, sure. Still not a good practice.

    I do agree that weld through primer is a good thing, just clean the proposed bead area 1st.