O/A welding sheetmetal

[mrbprint]

I am a licensed aircraft mechanic who had 5 weeks of O/A instruction in school on thin wall tubing, but welding 20ga sheetmetal with a torch is mind boggling. It would seem the heat affected area from even a 0 tip would be far greater than a mig, yet most of you prefer it.

Even now 30+ years later with only occasional use I am much more comfortable with a torch than a mig or stick welder. Any tips on its use. I am looking at welding in 2 rear quarters on my Galaxie and each has about 8' of seam to do. I have been practicing with my Lincoln 140 mig without much success yet. Early in my career I welded an aluminum taxi light housing with O/A using a tip I picked up from PM. I used a scrap of metal as filler and the soot of a carburising flame as a temp indicator. It wasn't pretty but it held till we could get a new light. Maybe I'll start practicing with the torch.

[Rick (madera)]

I use a OOO tip on my O/A to weld 19 gage:)

[timothale]

I was watching my nephew doing jewlery repair in his shop. He used a hypodermic needle for a small tip. He starts a flame on his regular tip. puts out the flame and sticks on the needle on the hot torch it.. melts the plastic and seals . when he is done welding the intricate pieces twists off the needle tip with a pair of pliers. he has different temp alloys in little squares, he starts with the higher temp and works down the temp range so the welding heat won't make the piece fall apart as he builds the jewlery.

[59flatbedford]

well i redid the floor in my 59 f100 using a torch and you just have to go slow with. just spot then stretch spot the stretch. if you do a search hopefully the old threads on perfect weld seems are still around. I am now redoing the floor in my 59 again (i didnt know crap when i did it the first time) and have bought a miller 130 mig that i will be using. for mig i think it is best to turn the heat up a little and the speed down some so as to get a flatter weld with less grinding required and you still have to follow the same process of spot and stretch.

[kenc]

Trouble is, we'll all have different ideas of what's the right tip based on our technique.

Rick's 000 is waaaayyyyy too small for me, but just right for him. 000 is a #75 drill size, it would take me all day to weld with that. In Smith sizes I use an AW202 which is a #69 drill size or about two and a half times the flow rate of Ricks.

You've got to "suck it and see" I'm afraid.

[mindover]

Gas welding is the traditional method that has been used for for generations for joining car body panels, its not the only way, its not even the best way for every case but it works very well if done properly. The cause of distortion is not so much the amount of heat that goes into the panel as how even the heat is. If a piece of metal is heated it expands, as it cools it contract beyond it original state. If it is heated evenly it will expand and contract evenly and little distortion will be caused.

Richard ( The rod doc) showed this in another thread using tig welding.

Below is a photo of a weld done by my employee James whom I taught to weld using the traditional method I use. This weld was done with gas.

http://metalmeet.com/forum/picture.php?albumid=96&pictureid=1013

[mrbprint]

I am going to dig the torches out and give that a try. It looks easier and more controllable than mig. Thanks guys

[ShawnMarsh]

I am going to dig the torches out and give that a try. It looks easier and more controllable than mig. Thanks guys

I have never found O/A welding to be easier than MIG, but it certainly is a softer weld which you don't have to grind down for hours lie a long MIG weld.

And David, that weld that James did is BEAUTIFUL. That is an extremely even heat band...I thought mine were pretty even with a TIG, but wow, that is pretty.

[RedBeard66]

nice heat zone! i've never seen a gas weld with such a small one!

[mrbprint]

I hear many of you say how hard a MIG weld is. Are you using mild steel wire or the hi-tensile wire for uni-body cars? What would make a MIG weld harder other than the filler? I agree- that is a gorgeous weld.

[mindover]

Yes James has become good! Mig welds are harder I have learned on here because of super-heating. Its the rapid heating and cooling of the weld apparently.
The advantage of gas over mig is no grinding of the weld, it takes relatively little work to dress out and combining this welding technique with proper placement of the welded joints means a good metal finish. below is the car that the previous photo was of (1938 BMW) the finished panel can be seen. The rest of body was not finished at this stage.

http://metalmeet.com/forum/picture.php?albumid=96&pictureid=1020

David

[mrbprint]

Nice work. Last year at the Rhinebeck,NY car show and swap I overheard a couple of guys talking about massaging a replacement rear deck lid for a 34 Ford roadster to fit. Now I know what they were talking about. This is a great site.

[ESjaavik]

I hear many of you say how hard a MIG weld is. Are you using mild steel wire or the hi-tensile wire for uni-body cars? What would make a MIG weld harder other than the filler? I agree- that is a gorgeous weld.

The MIG wire have to be stiff (hard) to feed through to the mouthpiece. I guess that have something to do with it as well as the rapid cooling mentioned. As I see it MIG is fine if all that is needed is to grind it. But hammer and dolly gets marked up. I don't know what those saying this does not happen are doing differently than what I do.

When it comes to OA tip numbering they are different between manufacturers. Maybe you could measure the hole in your tip David? If you have drills in 0.1mm increments you can use the shank as a measuring tool. But check the actual diameter of the shank, usually it is a tiny bit smaller than the drill size.

[larry mullen]

hello
just got done welding fender piece up using OA . The weld did not seem to penetrate completly in spots on the seam . I ended up welding both sides.
Larry

[Peter Miles]

The MIG wire have to be stiff (hard) to feed through to the mouthpiece. I guess that have something to do with it as well as the rapid cooling mentioned. As I see it MIG is fine if all that is needed is to grind it. But hammer and dolly gets marked up. I don't know what those saying this does not happen are doing differently than what I do.

When it comes to OA tip numbering they are different between manufacturers. Maybe you could measure the hole in your tip David? If you have drills in 0.1mm increments you can use the shank as a measuring tool. But check the actual diameter of the shank, usually it is a tiny bit smaller than the drill size.

Although I don't have the welding experience myself to back this up, keep in mind that many people use MIG wire for TIG welding. To the extent that TIG welds are considered softer than MIG welds, that would seem to imply that it is the differences between the TIG process and the MIG process that accounts for the weld differences if they are using the same filler.

Does anyone use MIG wire with OA welding?

[mindover]

hello
just got done welding fender piece up using OA . The weld did not seem to penetrate completely in spots on the seam . I ended up welding both sides.
Larry

Larry what process are you using to weld? If you don't have penetration it is because you are either using too small a tip or moving too fast.

David

[larry mullen]

hello
peter funny you should ask about mig wire for OA welding . Thats what I used .o45 wire . Also the tip size is 0 ,david . I,m out of practice with OA ,Not much of an excuse ,right ;). I notice in your Dvd u use no filler rod . need to get back out there and do some coupons. .
Larry

[mindover]

hi Larry, the reason I weld without filler rod is that it means that I can get a narrow, even HAZ as shown above. This keeps the distortion to a minimum. Its worth a try!.

David