When I decided to undertake this project -- mind you, I'm still in the feasibility phase -- I decided that the time had come for me to learn how to weld. The shop had a couple of welders, a huge old Miller tig welder and a new little Lincoln. It turns out the big unit, which had been donated, was so old it was hard to find the pieces needed to get it going. That left the Lincoln, a Wel-Pak HD flux-core rated at 35-88 amps.
After spending several hours trying to weld pieces of scrap sheet-metal together and getting nowhere I started to ask around. I was told that the Lincoln was not a good match for auto body sheet metal work. As soon as the work became hot enough to bond it burned through, and the flux-core wire was spitting gunk all over the weld area that interfered with the bond. One guy said it was designed to weld 1/8 in. steel, not thin sheet-metal.
One system recommended by GasPro that looks good to me is the Miller Millermatic 140 with Auto-Set. This unit can be used with inert gas, something the shop's Lincoln lacks, and is rated 30 - 140 amps. Miller claims it can weld mild steel from 3/16 in. all the way down to 24 gauge, thinner than the E9's body panels. Base price $789.00.
The slightly larger Miller 180 looks like a good machine. Same capabilities with more power but without the automatic setup, for about $200 more. Problem is, it requires 220 volts, and the only 220 outlet on the shop floor is nowhere near my bay.
Lincoln also sells a 120 volt MIG welder rated at 140 amps. The 140T uses a tapped transformer and is limited to a stepped output, while the 140C is continuously variable. The web page hints at why I am having so much trouble: "... for MIG welding on thin gauge steel, stainless and aluminum. Or, use gas-less flux-cored welding for deep penetration on thicker steel, even outdoors!" See that part about no gas and flux-cored wire? That gives better penetration on THICKER steel. We have to guess how thick thicker is, but it appears to be thicker than thin.
The July 2007 issue of Popular Mechanics, the engineer's bible, has a story on doing rust repairs using epoxy instead of welding ("No-Weld Rust Repair," John Decker, pg 119). The basic technique is the same. After cutting away the rusted area you install a backing plate, then install the patch. The difference is that in place of welds the pieces are stuck together using epoxy. Messy, but it saves buying a welder and eliminates panel warping caused by the heat of welding. Something to consider, especially since for years aircraft have relied more on glue than rivets. Here are some likely sounding products: Smooth-On and LORD Epoxy Adhesives.
Some old skool guys prefer to use gas welding for automotive body work. The attraction is that the weld rod can be so similar to the sheet-metal that after filing and sanding you cannot see the weld. The down side is the likelyhood of heat warping.
Whichever way I decide to go I need to decide soon.
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2 comments:
I have an entry level Lincoln MIG welder. I have tried stick welding (electric arc) as well as brazing, and the MIG is SO much easier.
I bought the welder used on EBay for something like $100 dollars, and it has been great. I wouldn't go too crazy buying a bigger welder, because really the majority of your welding will be on sheet metal stock, and not heavy gauge frame members, etc.
Like so many other things, your success relies mainly on the preparation. If the 2 peiced you are welding are clean, shiny, and rust free, you will have almost no problem getting a good weld.
As for panel warping, I use a succession of tack welds, working from opposite ends toward the middle. I haven't developed the skill to run a bead, completely filling the edges of a patch. In most cases, you will need to fill the patch with a little body filler anyway, so the gaps between the tack welds provide a place for the filler to grab, a sort of mechanical bond for it.
There are also plug welds that Malc has made extensive use of. They are also very valuable and pretty easy to master.
Get a MIG welder. Don't believe the hype about flux core welding. The MIG gas makes it so much more effective.
Keep at it. And keep those pictures coming.
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