TIG Welders

[crash]

I am in the process of working on an old vehicle, and need to fill alot of holes that had been previously drilled into the body for varying reasons plus have to weld in a few patch panels, with material no thicker than 1.5mm.
I have a MIG, but my research has lead me down the path that TIG is better for body work as the weld is "softer" than a MIG and easyier to work afterwards when compared to the MIG.
I would only want the TIG for lighter things, and save the MIG for heavier material.
What sort of features should I be looking out for, and any brands that should be avoided.

[steveG]

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

[Carnut1100]

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.

[Bigbjorn]

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".

[Slunnie]

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.

[Richard93Vogue]

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 :D

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.

[lokka]

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

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 :p

[crash]

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.

[flagg]

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


as in on / off, amps up / down?

[crash]

as in on / off, amps up / down?
Yes I think that is what it is suppose to do, the instructions make little sense to me at the moment.

[flagg]

Yeah I find torch controls frustrating as really you need to hold the torch differently for each run depending on the profile / angle etc and my fingers rarely are in the right place to use them.



Pedals are the bomb but are $$$. I don't have one for my new BOC as online the best o could find one for was about 400 euro! :(

[justfishing]

Hello,
The 4 way switch is a trigger lock one touch on, touch again off, you do not hav eto keep holding it on. 2 way is holding it on to keep welding.
There are lots of trick to welding panel steel to keep distortion down is as soon as you have finished welding put a wet cloth on it as soon as possible you can use silicon bronze rods a little less heat. Me with panel steel I use my MIG and spot it ( pull trigger a second then release) then no distortion at all especially on holes like you have.
Ian

[lokka]

Depending on the unit you have with the 2T and 4T settings for the torch trigger there are a few added bonuses like hot start or slope up at the start and crater fill or slope down st the end of the run

I use a trans tig 200 ac/dc unit it has all the bells and bits and using it on ally i use the 4T function as follows
Push and hold button down i get a hot start i usually set at 30% more than base amps
Release trigger slopes back to set base amps which i can now control at the tip of my finger via a roller control in the torch whilst laying my weld as this is great for ally as it heats the job up less amps are needed
Push and hold trigger for slope down and ad a bit of wire at the end so i get a nice rounded off weld finish instead of a scalped out tail

As for pulse welding its a whole other art and once mastered you can time the dip of wire to the up slope of the pulse and get robot looking welds its amazing what you can do with a good tig and plenty of practice and patience :D

[crash]

Release trigger slopes back to set base amps which i can now control at the tip of my finger via a roller control in the torch whilst laying my weld as this is great for ally as it heats the job up less amps are needed
:D
I noticed I have a small "slider" switch on the gun, which I am going to presume is a small controller like you have mentioned.
Un fortunately I have had to put the TIG away now for awhile as I can focus a bit more on a different project. Will have to do alot more practice before I tackle the sheet welding I bought it for.