to poor for mig

[Chickenjohn]

I don't know anything about arc welding, however, I do know a bit about welding car bodywork using Mig and Oxy acetylene gas welding, and from this knowledge there appears to be a flaw in your argument.

You said that in the days before Mig welders that people must have used arc welders on thin metal:- "but after much reading it dawned on me that arc welders have been around much longer than migs, and they must have been used on thin metals."

Not quite right, before Mig welding was invented (2nd world war time, I think), the major welding method used for thin metal was Oxy Acetylene gas welding. Using a 1mm nozzle, it is a great method for butt welding thin sheet steel such as used in car bodywork, and is the preferred method on good classic car restoration courses for visible panel work.

With gas welding you can weld a repair piece in without using any filler rod, provided your repair piece perfectly butts into the work, with no gaps. Of course, filler rod can be used to bridge any gaps that are present. This technique will give, in skilled hands, a much neater result than Mig and has the bonus of being a "soft" weld that can be dressed and planished to shape much more easily than mig.

So, before Mig, there was gas.

 

[GeorgeB]

I just found the missing image in my series of arc welding photos from about a year back. My first image in this thread (previous page) was of a near-continuous line of arc welding tacks to join two pieces of 0.8mm sheet metal. The photo here is of the arc welded seam which I placed on top as the next stage. In top professional welding, they frequently build up layers of weld, so I'm sure it must be a reasonable appproach. In my opinion, what you end up with, looks almost as good as a good MIG weld, and better than a bad MIG weld. I'm sure it's as strong as a good MIG weld and it's certainly cheaper. My point on cost relates back to Ned's opening post. My car sill welding went wrong because my butt joints had too many gaps. I needed to add masses of new metal to bridge and fill all the gaps.

 

[grandads_shed]

what rod did u use ???

 

[GeorgeB]

what rod did u use ???

Aldi 2mm 6013.

 

[wyn]

Out of interest i had a bash on some 0.9mm sheet this afternoon. A lap joint with 1.6 rods at about 30 Amps. I clamped it to some aluminium bar to take some of the heat away. This was done with an inverter, i think it would be tricky with a transformer type arc welder.

 

[GeorgeB]

Wyn - your joint looks very good - much better than my attempts. Do you agree, it's perfectly achievable? If only I could have produced a lap joint like that on my car sill...

 

[runnach]

You have to remember George, that is one chunk of a heat sink Wyn used to reach a reasonable standard..................

 

[wyn]

Yes George it is achievable but i could imagine that it would be tricky actually on a car.

 

[oilcooled :)]

very nice weld, is that a 1.6 mm or a 2mm rod that you ran the seem down with?

 

[brightspark]

try tack welding it first then run the weld without heat sink behind. u will find u can only run about quarter of inch and let it cool down .then start again otherwise it will get red hot and burn holes then show us results

 

[wyn]

It was a 1.6 rod, oilcooled.

You're right there brightspark..the rod didn't really work under 30 amps, so without the lump of aluminium it would have burnt through pretty quickly.

 

[brightspark]

It was a 1.6 rod, oilcooled.

You're right there brightspark..the rod didn't really work under 30 amps, so without the lump of aluminium it would have burnt through pretty quickly.

not that i profess to be able to do it myself as i tried 30 years ago and gave up just learned to do gas welding instead for thin work

 

[shenion]

I found it easier with 2mm rods. My 1.6's need to run at higher currents.

Have done 1mm butt weld with no backing. Not to bad with 7014 rods. Was too lazy to drag mig feeder out to driveway.

The rods make a big difference. My arc has 90 OCV and can go down to 5A. The rods limit the lowest current more than anything.

 

[oilcooled :)]

plus if the metal your attaching on to was .8mm new, it may only be .6 or .5 now on any weld repairs on cars making the job even trickier for arc

 

[GeorgeB]

You have to remember George, that is one chunk of a heat sink Wyn used to reach a reasonable standard..................

Yes, you're right. A base/backing plate like that would be hard to arrange for most jobs on a car. Not only would the block act as a heatsink but it would prevent any holes blowing through, simply because any molten metal has nowhere to go. It's still impressive, though. I used no backing plate or heatsink for the joints I displayed.

 

[Bsmith]

If using an inverter or other dc supply you can have the rod negative to help avoid burn-through. Welding vertical down also helps but a bit difficult to have a car sill in that position.

 

[oilcooled :)]

this came into mind in the back of a theoretical mechanics class in the i.t
i may get shot for saying this any way i will say it. firstly mig tig or gaz welding brazing is the way to go on thin section. however i have never tiged or miged, spend twice my youth at arc and a slight bit of a while at gas. seeing as welding rods cant be got below 1.6mm, and inverters go to well bellow 10 amps could a man cut a strip of gasless wire about 4" inch long . . . . and insert it into the striker and weld thinner again or is that as daft as a box of frogs??

 

[Bsmith]

this came into mind in the back of a theoretical mechanics class in the i.t
i may get shot for saying this any way i will say it. firstly mig tig or gaz welding brazing is the way to go on thin section. however i have never tiged or miged, spend twice my youth at arc and a slight bit of a while at gas. seeing as welding rods cant be got below 1.6mm, and inverters go to well bellow 10 amps could a man cut a strip of gasless wire about 4" inch long . . . . and insert it into the striker and weld thinner again or is that as daft as a box of frogs??

I think it would melt instead of arcing at the tip.

 

[GeorgeB]

I think it would melt instead of arcing at the tip.

Yes, I tried last year and it just 'heats up' and blows like a fuse.

 

[Country Joe]

Yes, I tried last year and it just 'heats up' and blows like a fuse.

Excellent, guys - I'm not the only one to try this kind of thing!
Next time I look up & see Mrs. Joe observing one of my "experiments", I can come out with "I know that other people try out things like this" - without feeling like a liar!
I suppose I was sort of lying, as I only almost knew. But that was then, now I really do know!

Nice one, fellas!
CJ