Thread: TIG Welders

I'm no bodywork expert, but from my limited experience TIG puts a lot more heat into the job than MIG, so I'd expect more distortion on panels. Pretty sure most panelbeaters use MIG's.
Easiest way I've seen to fill holes is to use a MIG with a copper block placed behind the hole.

I've got a 200A Mitech AC/DC TIG which I'm pretty happy with. No need for the AC side unless you want to weld aluminium. Mine is HF start whereas I think the cheaper DC only machines are scratch start. I've never used a scratch start one, but the HF start is really easy - touch the electrode to the workpiece, then lift it slightly and press the trigger. to start the arc.
You will need a bottle of argon to run the TIG (ie you can't use Argoshield etc that you're using for the MIG).
Get some TIG gloves too as the usual heavy gloves you use for MIG/MMA don't have sufficient feel to feed the filler rod nicely.

Something to keep in mind is that you need a nice still environment for TIG. I got caught out last week modifying an old sill tank in my shed. Found myself struggling with weld porosity and figured it was some sort of contamination in the original material.
Finally worked out I was welding quite closely to the welder itself, and the cooling air was creating a draught that was blowing the gas shield away. Hung up a blanket as a shield and no more problem.

Steve

Most crash repair places use a MIG and a spot welder to do panel replacement.
Panelbeaters (of which there are precious few today) use TIG or oxy-acetylene as the weld is indeed softer and it can be beaten and worked unlike a MIG bead which is hard and will crack if beaten much. All you can do with a MIG bead is grind it down.

Yes a TIG puts more heat in the panel but nothing like oxy.
There is potential for distortion but the distortion is easier to correct with a hammer and dolly while MIG distortion is almost unfixable despite there being less of it.
Also the skill of the welder makes a big difference. Get good enough and you can weld coke cans together...

The ideal bodywork TIG or Oxy weld is only marginally thicker than the body metal then it is dressed down with a dolly and planishing hammer which removes the distortion (which is actually caused by the weld itself shrinking as it cools, not by the heat put into the panel per se) and leaves a tiny raised almost flat bead which is made completely flush with a gentle swipe of a body file.
Most people haven't the skill for that but that's the ideal.

Originally Posted by steveG

Something to keep in mind is that you need a nice still environment for TIG. I got caught out last week modifying an old sill tank in my shed. Found myself struggling with weld porosity and figured it was some sort of contamination in the original material.
Finally worked out I was welding quite closely to the welder itself, and the cooling air was creating a draught that was blowing the gas shield away. Hung up a blanket as a shield and no more problem.

Steve

My instructor at technical college (before they were called TAFE's) used to repeat constantly to only use MIG indoors as "the beat of a butterfly's wings will disturb the gas shield".

Originally Posted by Brian Hjelm

My instructor at technical college (before they were called TAFE's) used to repeat constantly to only use MIG indoors as "the beat of a butterfly's wings will disturb the gas shield".

They're not too bad now. You can get different shrouds if you're MIG welding outside, but as you say, they still dont take much of an airflow to shift the gas shield.

To help with distortion whilst using TIG it is essential to do frequent tack welds along the length of the section to be welded. Sometimes that can mean every 25mm along a long section. This proceedure gives structural rigidity and helps keep the panel/section in place while you go back and do the rest of the work, which on thinner material can still mean just stitching up between the tacks and spreading the load around to prevent too much localised heat.

Can be time consuming to start with, BUT the results are much more satisfactory

Sometimes (certainly not always!) filling holes can be helped with a 'low tech' idea of a few damp/wet rags placed strategically around to deal with some of the heat as it happens.

Richard.

Richard is on the money slowly slowly bit by bit and a wet rag

That goes for both TIG and MIG on body work tho if you want soft welds with MIG get some silicone bronze wire it works well and wont rust and is easy to shape and file

As for out door welding either turn up the gas flow or throw a welding jacket or woolen blanket or even an old fire blanket over your head and the welding area and your right to go

Tho for filling holes and patch work in a rover pop rivets and patches will be fine a few more rivets in a series wont bother it

I ended up buying a Tech Weld A160 TIG / Stick welder, with HF start. The other choice was a BOC machine but for an extra $70.00 over the BOC I got a few extra features like variable pulse, adjustable post flow, ramp up and ramp down. I am glad I spent the extra.

I have to admit TIG welding has me amazed and love it. I like the fact that you can weld without filler wire as well.
Pulse welding definatley has its advantage on thinner material.

I have not been able to work out the advantage of the 4 way switch.
Still doing alot of playing. My butt welds have been good, but my lap joints require more technique. Have yet to try corner welds.

One thing for sure is I am having fun with it.
Lots more practice required.

Originally Posted by crash

I have not been able to work out the advantage of the 4 way switch.

as in on / off, amps up / down?