TIG Car Bodywork

[candygt]

Hi guys,

Just wondering if anyone has any tips for welding car bodywork with the TIG.

My model is DC, goes down to 15 amps yet im still blowing holes on the edge of panels which are 1mm.

Is it not possible to butt weld such thin metal..? I thought I was supposed to be using approx 25 amps however that blows through even quicker when I get near the edge. I thought 15 amps seemed better but when I add the filler the weld pool seems to cool very quick leading to stuck filler rod.

So.. tips please

 

[hotrodder]

Machines vary and user technique (arc length and travel speed) have quite an effect but i typically run 29-35A for 18 and 20 swg (just either side of 1mm) butt welds using 1.0mm filler wire or some 0.8mm MIG wire (straighten it by spinning it with a drill while under tension with the other end clamped in a vice). 1.6mm wire makes life more difficult in that it requires more heat to melt than thin bodywork i.e. either end up with the puddle freezing each time you dip the wire or needing more amps. Also kinda defeats the purpose in that the advantage with TIG or oxyfuel is the minimal weld reinforcement possible i.e. a bit longer to weld it together but little to no grinding of the welds

General technique for TIG coachwork would be to tack the part together tweeking fit (dollying where necessary) and adding tacks until the patch is tacked at half to 1 inch intervals. Final weld done in one inchish runs using a combination of skip and backstepped welds. Short arc length and sharp tungsten are very important regardless

Edges will be prone disappearing quickly, a few extra tacks can help and depending machine can also turn the amps down a touch for them- manually, with slope out controls or via a foot pedal. Could also make use of a heat sink i.e. clamp a chunk of ally or copper to the backside of the edge. Slope up can help prevent blowing holes while tacking. Machines without this, especially 'scratch TIG' make life a little harder with thin stuff- can either strike up to the side of the joint and move once the arc is established or lay the filler wire on the joint and arc up on that, doesn't work so well with fine wire but if using 1.2 or thicker stuff...

 

[backpurge]

Candygt
Hotrodder's advice is excellent stuff and can't really be added to, my only comment is that TIG would not be an automatic choice for vehicle body work, you will find MIG far better

 

[candygt]

Many thanks for your speedy reply. Some great reading there, thanks for taking the time to post the link aswell.

Unfortunatley using a heatsink on the rear is not an option due to the location of the weld.

I would love to use a MIG however the only one I have available is a friends gasless model and it hasnt proved useful for bodywork yet.. I think the combination of lowest settings + gasless = still to hot! Thus my reasons for choosing TIG.

I think my limited skill in fabricating the patch is not helping either.. definatley could have a tighter, more uniform gap.
In the end I resulted in fitting part of the patch slightly recessed using a lap weld technique and plan to build up using primer. I know its not ideal but having cut a hole in the car.. its gotta be fixed!!


.. its still far from finished :P

 

[hotrodder]

A poorly fitting patch will definately make life more difficult, even more so with TIG than with MIG. Really want a daylight tight fit, certainly less gap than the materials thickness for thin stuff. There's various ways to go about making a patch panel, some probably covered in the MIG tutorial section. Typically start out with a slightly oversize patch, if both sides of the panel are accessible then can mock the patch in place (tape, magnets etc) after removing the rot and scribe the final trim line using the car as a guide. If the panel is double skinned then again make a slightly oversize patch but scribe the car for final trim. In either case (assuming tinsnips for final trim) if there's more than 1/4" of material to be removed take a roughing cut first. Min cutting width with decent quality snips will be around half the material thickness

 

[squazy84]

yea my dad insisted his first try on my new tig would be upside down on the runner sill of a car that needed a patch and made a very rough patch with big gaps and proceeded to blow holes in it then get ****** off and get the oxy accetelene and braize the patch gaps included,tig just aint as good as i hoped where large gaps and little expierence are concerned!

 

[langy]

I use TIG for bodywork and hotrodders advice is spot on, the MIG would be easier for you, I use TIG as I can hammer weld the panels which you can't do with MIG.

 

[madkayaker]

whats hammer welding ?

 

[hotrodder]

Welds shrink which results in distortion. Big gaps (while easily weldable with practice) means a lot more weld metal = a LOT more shrinkage and distortion. Hammering 'on dolly' stretches metal relieving distortion. Hammering while hot can also be used to shrink metal- the surrounding cold area acts as restraint in two planes leaving the metal only one choice, to shrink into itself getting fractionally thicker. Weld a patch panel in and there'll be some distrotion from the shrinkage while the weld bead itself will typically be high with too much metal. A bit of hammer and dolly work can flatten the weld bead some and eliminate the distortion

MIG welds typically have too much reinforcement for hammering to have much effect (or at least positive effects), the size of the weld bead prevents the panel being 'read' properly anyway. Welds also harder because the process is colder

Oxyfuel typically leaves the panel the most workable but there's usually more distortion to deal with. Sometimes for the really talented can be the way forward i.e. can deal with an 'oil canned' mess of a panel while patching rust holes/the really mangled bits

Obviously depends on what's being done to what standard but I tend to view TIG as offering the best of both processes (most of the time) for restoration in that weld reinforcement can be minimised and the result is immediatly workable with hammers 'n dollies. While not as workable as gas welds there's less distortion so swings and rounabouts most of the time. More distortion than with MIG but less, maybe no grinding and given the choice i'd rather spend 1/2 hour with a hammer and dolly than 1/2 hour with a grinder. Of course if patching the daily to get it through the MOT, plug welding floors or dealing with double skinned areas that have no access for dollies then MIG makes far more sense

 

[langy]

I was just going to say i hit it with a hammer nice explanation.

Welds shrink which results in distortion. Big gaps (while easily weldable with practice) means a lot more weld metal = a LOT more shrinkage and distortion. Hammering 'on dolly' stretches metal relieving distortion. Hammering while hot can also be used to shrink metal- the surrounding cold area acts as restraint in two planes leaving the metal only one choice, to shrink into itself getting fractionally thicker. Weld a patch panel in and there'll be some distrotion from the shrinkage while the weld bead itself will typically be high with too much metal. A bit of hammer and dolly work can flatten the weld bead some and eliminate the distortion

MIG welds typically have too much reinforcement for hammering to have much effect (or at least positive effects), the size of the weld bead prevents the panel being 'read' properly anyway. Welds also harder because the process is colder

Oxyfuel typically leaves the panel the most workable but there's usually more distortion to deal with. Sometimes for the really talented can be the way forward i.e. can deal with an 'oil canned' mess of a panel while patching rust holes/the really mangled bits

Obviously depends on what's being done to what standard but I tend to view TIG as offering the best of both processes (most of the time) for restoration in that weld reinforcement can be minimised and the result is immediatly workable with hammers 'n dollies. While not as workable as gas welds there's less distortion so swings and rounabouts most of the time. More distortion than with MIG but less, maybe no grinding and given the choice i'd rather spend 1/2 hour with a hammer and dolly than 1/2 hour with a grinder. Of course if patching the daily to get it through the MOT, plug welding floors or dealing with double skinned areas that have no access for dollies then MIG makes far more sense

 

[madkayaker]

thanks

 

[busastars]

Personaly for car work I would use a mig, easyer to do tacks and got a hand free. I can weld 0.8mm at around 30A on my el'cheapo Giant tig but if there are gaps because of the fabrication then its a pig to do.

I tend to strike or start the arc away from where your weld needs to be and then move across to where you want it, say 30mm away. Also the at the joint I have a some mig wire there waiting to take the first part of the weld. On thin stuff I will genuraly use mig wire as my filler. On thick stuff genuraly I dont need it just fuse them together, not quite as strong but depends what you are doing and what it is for.

 

[candygt]

Have recently got myself a MIG aswell as the ArcTIG and I have to say its amazing for bodywork.

I have seen the light!

MIG for the car every time now!