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Best Method to weld sheet metal repair panels in...

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doc50

doc50

Jedi Trainee
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Hello all, a newbie here. Have my latest 'obsessive compulsion', a '59 TR3 that is in several boxes and piles. I have donor side 'tub' sections and am ready to 'cut and paste' some rust areas.
My question is simple:
1) what method should I use to weld these sheet metal parts in: butt weld or overlapping (after all it IS thin sheet metal, so I think door and fender tolerances won't be too badly affected)?
2) what type of welding, ie; mig or oxcyacetylene?
3) if oxy, what metal to use, brass rod or steel?

Randy Shultz, who widened his TR3 by 4" suggests a method I am not familiar with, in which he apparently does not use ANY rod with his oxy welding, just heats up the tight butt joint and smooths it all with a hammer and dolly. Any thoughts on this method?

Thanks for any thoughts!

Thom
 
Hi,

Firstly, welcome to the forum. I'm sure you will find lots of friendly folks and useful information!

I have been using MIG to do patching with the thin sheet metal. Most auto body shops will use MIG. You don't want to use oxcyacetylene or gas welding on sheet metal because it imparts a lot of heat into the panel and will cause it to warp.

If you use a butt joint or an overlap (lap) joint, will depend on your ability, the size of the piece etc. A butt joint takes more skill and work as you have to get a good fit between the patch piece and the panel you are patching as opposed to a lap where the fit doesn't really matter . Personally I'm lazy so I use mostly lap joints.

Once you've welded in the patch and ground the weld beads, it's a good idea to cover it with fiberglass filler, to make it water resistant.

There are a lot of good videos and sites that have step by step tutorials on how to weld if you "Google" it.

Cheers
 
Check the video on this page. https://www.mig-welding.co.uk/thin-metal.htm

I've used this technique to butt weld on 20 gauge. I think before rust the TR is probably 18gauge. Get some scrap material and practice, practice, practice. Mig is probably the easiest way to go.
 
Off hand, I'd have to say "yes" to all the techniques. In patching body panels, each method has its use, so you eventually have to learn them all. Of course, it's also forgiving enough to use just a couple in a pinch.

The hammer welding is a PHD level skill!
 
You will find mig on a lapped joint best (easiest). Northern and other outfits sell a pnuematic hand held flanger/hole punch that will drop flange the edge of a repair piece. You would cut out a bad spot on the body you are using and cut the corresponding part out of the donor body about 7/16 inch too big overall, flange the new part, and insert it in the hole to be repaired. The flange relieves the surface height by about the thickness of the panel. You can, of course, flange the receiving panel if there is room for the tool and drop the flat repair panel into the donee panel. The punch will make holes that can be used to weld thru, making sort of a spot weld. Weld short beads and let the metal cool to avoid warpage. be very careful of this practice. Overheated metal will expand permanently. On butt joints, when you fit up the weld you can back the joint with copper sheet to avoid burn thru. The copper will not become involved in the weld. TAKE A WELDING COURSE IF YOU ARE NOT ALREADY PROFICIENT. I did. On cutting holes and patches, the little cutoff wheels sold for dremel tools are very useful
Bob
 
Butt weld with a MIG is better even for beginners, IMO. Just takes some practice to maintain the arc. On a lap weld a beginner is tempted to build up a bead to "fill" the seam, in addition to welding the punched holes. Carefully fit the patch, tack in a few spots, then weld the seam in short sections at low heat and relatively low wire speed. Definitely recommend getting a MiG with a gas bottle, the welds will be much better and cleaner.
 
Thanx all, I understand there are several situations that require different solutions. I will butt joint my panels and try to make them look OEM. This will take more time but I think it will be worth the effort. Now to fire up the Hobart 140 to practice!

Thom
1959 TR3
 
I will also weigh in on the flux core versus gas, go with the gas.
 
Do not forget body panel glue! No worries about panel warp. Very common in auto body repair. It does require good prep and a special gun. But it is fast and very strong.
Paul
 
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