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Thu Aug 15, 2013 11:48 pm

Noob question (obviously) regarding the proper way to combine/weld two panels that were originally spot welded at the factory. One panel I will be making myself (it's an under trunk support section) and welding it to a stock panel. These are hidden seams and each panel will have the customary 5/8" (or so) lip that would normally get spot welded together. Unfortunately I have no spotwelder so I'd imagine I could drill holes every inch or so [ON ONE panel ONLY] then use my cheap flux core wire welder to weld the holes and there by combining the two panels. Am I on the right track with that or not? Please give me suggestions before I screw something up :? . Thanks .

Fri Aug 16, 2013 1:22 am

What you describe is called a plug weld and yes a replacement for spot weld. You could also use a flange bending (google) tool at the joint.

The anti flux core people will be here soon enough but that can be done, it runs hot and you have to control heat for sheet metal. Also in theory a flux cored weld is more brittle than a gas shielded one but plenty of people do it, practice on like thickness sheet metal first.

I only flux cored once in a class long ago so others may have input there.

Fri Aug 16, 2013 4:53 am

Yes you are on the right track. A backer plate held tight behind the pc. you didn't drill will help with burn through. It can even be a pc. of flattened copper water pipe.

Fri Aug 16, 2013 11:04 am

OK "plug weld", I figured there'd have to be a name for it. Thanks for the tips, will flatten out a copper pipe and use that behind the spots. I know all about the draw backs to flux wire but it's all I have and I've read and watched videos explaining how to control the heat a bit. What size holes should I be drilling for the plug welds? Thanks again.

Fri Aug 16, 2013 12:48 pm

Try a 3/16" hole first then adjust bigger or smaller depending on burn through. Make sure the two pcs. are held tight together while plug welding.

Fri Aug 16, 2013 8:41 pm

Drill holes about 2" apart? ... or closer?

Fri Aug 16, 2013 10:02 pm

I have been plug welding my brains out lately on my 59 Ghia. Most panels I have worked on the spot welds avg about an inch apart, closer in sections such as bends or curves.
Make sure the two panels are clamped very tightly. The weld tends to push the two panels apart I discovered. I just clamp both sides of the plug, weld, then move the clamps to the next hole.
I also discovered that I had to make the holes around 1/4in. Smaller holes the weld tended to jump to the closer drilled panel and not penetrate the bottom panel enough. With the larger hole I could get the weld started on the deeper panel then fill the hole.
Eazy pezy 8) I never welded before a few months ago now I am weldin like a mad man now 8)

Fri Aug 16, 2013 11:28 pm

OK - on the same subject... I have some small rust pin holes (about 5) in an old original fuel tank, that I need to weld up. I have completely stripped the tank down to bare shiny metal already. This tank has not been used in many many years and no longer smells of fuel. However, I will be using water and baking soda on the inside of it, in the bottom of it - to keep an explosion from happening (a technique I recently learned of after research). So as for the pin holes.. should I enlarge these holes (to 1/4" possibly) to make closing the holes easier? Or just go at it, as is and try to build up some weld? It doesn't have to be all that pretty. The openings are too small to get any copper material behind the pin holes for heat dissipation. I'd rather not take it to a shop just for 5 tiny pin holes. Suggestions on the welds?

Sat Aug 17, 2013 1:52 am

Mmm - the pinholes are just the tip of the iceberg....the tank metal is rusted thin all around the pinholes. In other non-vw cases, I soldered the holes rather than weld. You can use brass cloth with the solder to reinforce weak areas. The real fix is to cut out the bad sections and weld in good metal.

Sat Aug 17, 2013 3:59 am

Ditto on the cutting out the bad areas. Then just overlap the patch about 1/4" all around. Make sure you cut to good metal. If you try to just weld over the pinholes most likely you will blow through the rusty metal.

Or find a good used tank.

Sat Aug 17, 2013 12:14 pm

On the tank rust pinholes, I also would be tempted to solder them. Welding or even brazing may blow right through the thinner metal around the holes.

Sat Aug 17, 2013 11:48 pm

if they are just pinholes a Por tank kit should fill most of them. there is also a tank repair kit for holes that is just JB weld and fiberglass. I had a pretty nasty tank that has been just fine for over a year now.

Sun Aug 18, 2013 7:17 pm

I got a Lincoln 140 welder and one of the options is a spot welder tip and a different circuit board.

What happens is...

You put on the special tip, set the timer on the new board (takes a little fiddling with wire speed, power, and the timer).
Hold the tip against the sheet metal and pull the trigger. It creates a puddle, burns through to the mating sheet, and just a split second before it shuts off, it retracts the wire just a little.

Works pretty good. I welded on the bottom heater channel plates (upside down) with about 400 or so welds in about 2 hours. And , I didn't have to pre drill any holes. I probably didn't have to put in this many but I'm sure it didn't hurt.

Sun Aug 18, 2013 7:49 pm

Danpa wrote: I got a Lincoln 140 welder and one of the options is a spot welder tip and a different circuit board. ...

...

Now THAT is nice! Can I borrow it?

Sun Aug 18, 2013 7:56 pm

Man I'm putting that Lincoln 140 at the top of my list for when I get a NON flux core MIG welder. For now I'm going to go the solder route.. been researching it and watching videos, looks pretty easy even with holes much bigger than pinhole size. Thanks for the welder suggestion though, your spots look great.

Mon Aug 19, 2013 2:59 am

Thanks, but it's all the welder. I'm mediocre at best as far as welding goes.