16 replies to this topic

[Lachlan]

Well, apparently my Brat has a few more rust spots than anticipated. That's ok, it just gives me an excuse to buy/learn to use metal working tools! Naturally I can't afford every tool in the shop, so I'm looking for advice on whether I should start with oxyacetylene or MIG welding. Here are some thoughts I have from information I've gathered:

OA Pros: cuts, shapes, and welds.
OA cons: Have to regularly refill gasses. May burn through metal if not careful.

MIG pros: cleaner welds. Not as much heat transferred into thin sheet metal
MIG cons: Still have to refill CO2/Argon from time to time (but can flux weld in a pinch). Can't see puddle as well. Needs separate equipment to cut or shape metal.

Any thoughts?

[Idasho]

Regardless of equipment, welding sheetmetal body panels is NOT easy.

That said, I have used OA on occasion, and will never use it for anything but heating/bending. In my opinion the only torch that should be near a car would be to braze. Not weld.

A good wirefeed mig is a fantastic investment. I have thousands of hours on my little Lincoln 135+, and all I run is flux core. It has all of the hoses and regulator to run shielded gas, but Ive honestly never seen the need. Clean metal, good ground, and a properly dialed in machine = clean spatter free welds.

As far as additional tools, for sheetmetal it really doesnt take much to get started. A small angle grinder with cutoff wheels makes for very quick work of large stuff. A good dremel does very clean work of sheetmetal. Without deforming it like many recip saws.

I have way more than that in my shop, but these are the things that I started with, and Im amazed to think now how much I actually accomplished.

[tallwelder81]

thats the ticket. if you go mig, dont go cheap. harbor freight isnt even worth the price if they were free. a power tool isnt worth cutting corners on budget,
cheap tools cost more than quality tools.

lincoln, miller, hobart.


another thing you may consider is a flanger.
looks like a vise-grip, but it has a wide L shaped jaw.
basically it just presses/bends a flat edge into a
45 or 90 degree fold, the way a lot of unibody
pieces need to be.

eastwood sells em, im sure lots of places sell em.
maybe 15-30 bucks.

a good strong rivet gun is handy for sheet metal work also.
around 35-50 bucks. maybe 75 for a nicer one.

[GeneralDisorder]

You DO NOT Want to use O/A to do sheet metal work. Especially working around a vehicle - the open flame is just not in any way convienent..... and the learning curve to weld thin sheet goods with O/A..... well I'm pretty handy with a MIG gun and I wouldn't even consider trying it.

O/A is for heating, bending, and cutting. Though sheet metal is best cut with plasma.

In my opinion, MIG (GMAW not FCAW) is the ONLY option for automotive body work. And with thin sheet metal it is imperitive that you have a decent quality machine - I would be looking for a Miller 110v MIG welder to do body work - or if you plan on doing more than just thinner stuff go with a 230v unit. I also like the Thermal-Arc offerings.

GD

[tallwelder81]

in my experience and word of mouth is this,
flux cores ONLY real advantage is in bad environments. windy, greasy, dusty etc....
and even WITH flux core, you ALWAYS want to prepare the surface as MUCH as humanly possible.

standard mig is the way to go.

[Lachlan]

Thanks for the input. I think I'll stick with the MIG welder for now, and maybe pick up a used torch later on for other projects. For you MIG welders, what size CO2/Ar cylinder did you buy? I see a 20 cu. ft. at HF for $100, or an !80 cu. ft. at the local welding supply store for $180. I think the smaller one would be more convienient for moving around the garage, but how often would I be going back for refills?

[tallwelder81]

i like the bigger bottle. and he said something about blah blah cheaper in a larger exchange.
you can see for yourself, the math doesnt even out.
20 for 100 is 5 per CF
80 for 180 is 2.25 per CF

[GeneralDisorder]

I have an 80 cubic foot tank myself. I can't imagine running one that's 1/4 the size. That would mean 4x as many fill-ups on my tank. No thanks!

GD

[Lachlan]

Thanks for all the information. I found a really good craigslist deal on some big O/A tanks (75cf Acetylene, not sure what the Ox is, but it's about 4-5 ft high), so I settled on a compromise. So I have the O/A outfit, and a flux core wire welder that I can upgrade to MIG when I get a CO2/Ar tank later on. I've already used the O/A to do some light brazing on the body (hood hinge fell off), and it works nicely. I also found that the torch is a nice supplement to an angle grinder in spots too tight to use a cut-off wheel. But I'd agree, I wouldn't weld with O/A on the body. The flux core is much faster, easier, and there's less collateral burning.

I've got some pretty big rust spots to repair now. If appearance is not a concern, what's the best thickness of steel to use to repair big holes and maintain rigidity?

[tallwelder81]

id just go with the original material. or maybe a gauge thicker.

i think subaru bodys were 20 gauge in the 80s. 18 gauge is easier material to find as scrap.

with the think stuff, the trick is to not go in a steady bead.

think of how an amateur teenager tightens his wheels lugnuts.

clockwise in a row. so it binds up and ends up a hair off-center.

youre supposed to stagger the tightening, bit by bit, yea?

same story with welding thin sheet.

half inch of weld, skip a full inch, weld a half inch, skip a full inch, so on.

when you are done with the length, and start over at beginning, it should have cooled sufficiently to hit it again, and after 3 passes, it will be continuosly welded.

like THIS: - - - - - - - not like THIS: -----------------

handy trick to use. otherwise you will burn through. also, THORUOUGHLY cleaning the surface is 80% of a good weld.

just like painting a car. the end results will only ever be as good as the initial prep work. most community college welding classes are perfectly okay with the average joe coming if for just one quarter, just to get a feel for it, with a certified guy looking over his shoulder now and then.

my school had lots of guys with no interest in becoming a professional welder, they just wanted to take a crash course for their own general benefit. and the teacher was fine with that.

just a thought......

[tallwelder81]

and THEY supply the gas, electricity, and very nice machines/equipment, and the actual steel sheets, plates, bars, tubes whatever.
that stuff ADDS UP FAST in costs.

i calculated it once in my head. the cost of it all, INCLUDING the cost of my gasoline to commute to school, really honestly came up even with the material costs. class was about 550-700 per quater. depending what time of year the quarter was, some are longer, i think winter quarter is almost 12 hours longer. the whole quarter was only 48 hours in the summer class. 60hours in winter.
and i bet i used up at LEAST 300 dollars just in metal. too hard to calculate all the electricity and electrode and shielding gas, etc etc etc......

its a lot. trust me.

[[HTi]Johnson]

A little late, but try to make sure any bottle you buy used isn't a rental bottle someone scammed from a Gas place. There isn't much crappier feelings than the one of trying to get your bottles filled and having the supplier say "These are our bottles, you can't have them back, unless you rent."

But yes, when welding sheet metal, you pretty much just want to do tack welds opposite of each other.

[Crazyeights]

If you have a local place in mind for refilling the bottle - you might consider giving them first shot at supplying one of their bottles to you. They might not be as pleased when you bring in a HF bottle and ask them to re-fill it. Again, just this is just IMHO. Good Luck:D

[Lachlan]

Thanks for the tips, guys. My local gas supplier doesn't care where you got your bottles from, as long as they're in hydro test. And I don't think they rent.

On another note, I picked up a brass earth clamp from HF (it was less than half the price of a similar clamp at the welding supp?y store). It has a waring about lead content from the good folks in California. Should I be concerned?

[GeneralDisorder]

On another note, I picked up a brass earth clamp from HF (it was less than half the price of a similar clamp at the welding supp?y store). It has a waring about lead content from the good folks in California. Should I be concerned?

I can't imagine it would be an issue unless you decided to chew on it.... probably shouldn't handle anything in your garage and then stick your fingers in your mouth either..... highly doubt it's going to off-gas the lead. :-p

I think you'll be plenty safe with your HF clamp.

GD

[Soobie-ruu]

The welding term used with sheet metal is called "stacking dimes" so you don't warp the sheet metal, in auto body they teach you to do a small weld like a circular tack weld every ten inches. Then wen you get to the end you start at the beginning so it allows Time to cool

[ferox]

On another note, I picked up a brass earth clamp from HF (it was less than half the price of a similar clamp at the welding supp?y store). It has a waring about lead content from the good folks in California. Should I be concerned?

HF sells a much better ground clamp made of steel with copper contacts. I would recommend it over the one you have just because of quality and performance.

The metallic lead content is those cast pieces from China is unknown. Your main concern is leachability. Lead hazard gets down-played a lot because it's an element, it's not volatile, an doesn't have a smell or taste per se, but it is bad news if you get poisoned. Most likely anything cast like that is also going to have other heavy metals like cadmium and chromium, so you may not get lead poisoning you may get heavy metal poisoning.

It's one of those things that isn't an immediate threat to human health and safety. It's an underlying hazardous condition that will get you once you are acustomed to the clamp and quit thinking about it.

I deal with this at work everyday, so that's my little PSA. I don't mean to sound dramatic or alarmist, but I would just get a better clamp and never have to think about it again. I am always surprised at how quickly and easily hand-to-mouth or hand-to-eye contact can occur.