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MG MGB Technical - Sheet Metal Butt Welding Clamps

Hi Everyone,

Does anyone have any experience with or opinion on the mini-clamps available for welding body panels?
These create a 1mm gap between edges to be joined. Manufacturers claim they reduce excess weld and therefore grinding requirements.

Is there a particular welding pattern one must use to prevent the consumable wire from just pushing through the 1mm gap?

The clamps allow a clean flush appearance but I've read that even low penetration settings on mini-MIG welders will become too high and leads to welds blowing through the joined metal. In the past I gently filed a v-section at the butt facing to improve weld penetration; this seemed to work. But are the butt clamps better than the v-section face method.

Thanks for reading,
Brian McIlvenna
Brian McIlvenna

Brian

Loads of good information on this site including welding technique videos.

http://www.mig-welding.co.uk/

One thing I have learnt - to minimise blowing holes in sheet metal make sure the wire coming out of the nozzle is hot to start with i.e. strike it up on a piece of scrap immediately before starting on the main piece.

Richard
Richard Evans

A mate who does heaps of specialty welding mig/tig uses an extra argon feed onto the back of his welding on real thin or special stuff. By doing this it stops blowing through,which he wouldn't do anyway, but the interesting part of doing this is that the argon stops the weld from coming out the back of the panel leaving it flush.
It's especially good for welding headers/extractors as it eliminates any dags inside the tubing where you can't get at it to clean up
On the gap question
1mm is probably a tiddle on the wide side from what I've seen happen- probably half a mm would be better for bodypanel steel
If you weld with no gap at all there is nowhere for the hot edge to expand to while welding and causes them buckles
Too wide a gap works opposite to this by needing too much filler wire in the welding process which will shrink back further than less weld as it cools and also causes wobbles in the panel
willy
William Revit

Guys,

Thanks for the input. It looks like the clamps may create more problems that than help. I think I'll revert to filing both butt faces to create a V-section, which will provide some gap and room for the weld to fill and hold. I'm sure the butt faces will not be perfectly straight so, to hypothesis, this may introduce some additional welcomed joint gaps.

I'm hoping the welding magnets should help keep the outside of the visible mating body panels as close as practicable to flush.

Brian
Brian McIlvenna

If you "V" the sheet you can turn the current down a bit! Weld penetration is a product of pool depth. The closer the edges are together the longer it takes to make a full depth pool. Having a joint gap makes full depth pool happen quicker. But then you have to be a better/quicker welder, but you can turn the amps down. I find
Interclamps on 20swg produce too wide a gap for my skill level unless it's a good day and horizontal!!!
Allan Reeling

If your mig has "stitch" option, give that a go
With stitch you still get the same amperage for your weld but it delivers in little pulses which reduces overall heat and the possibility of burning through
A bit more friendly for panel work
willy
William Revit

This thread was discussed between 07/03/2015 and 08/03/2015

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