Welding question
December 18, 2005 7:47 PM   Subscribe

Arc-welding or Oxy-Fuel welding?

I'm going to enroll in a class for welding and I'm trying to decide between Arc and Oxy-fuel classes. I'm looking to be able to weld bike-type components or general art, household welding. I'm also interested in whichever process would offer cheaper welding equipment. I'm not against taking the other later especially if they have their own advantages and disadvantages.
posted by drezdn to Education (9 answers total)
MIG is the best general purpose, you'd need to be a wizard gas welder to weld bike frames without distortion. Flux core mig is cheaper and can be used outdoors easier; gas mig is more versatile and makes nicer welds. A gas rig is good for heating/melting stuff but you hardly need a class to figure that function out. Either way when pricing stuff out don't forget gloves and helmet. You'll also probably need a 4-4.5" angle grinder for cleaning and chamfering.
posted by Mitheral at 8:03 PM on December 18, 2005

I took an arc class about 10 years ago; it was pretty easy to pick up (and I am a classic clumsy nerd.) Some of the better students were fooling around with MIG by the last session. As Mitheral says, gas can be tricky -- our instructor, who had been welding since before WWII (a real old timer!) started everybody on arc and treated gas mostly as a curiosity. I'm sure there are certain applications where gas is still the best choice, but I understand the learning curve for gas is much steeper. Anyway, arc is good for strong joints in heavy materials but if you want to work with sheet metal or certain specific metals/alloys you'll eventually need to tackle MIG.

If you do choose the arc class a welder's jacket is a good purchase -- hot stuff will be flying everywhere, espeically as you're learning, and the sparks can trash (expensive) or burn through (ouch!) pretty much any non-specialized jacket. And unless you plan on doing A LOT of welding you can probably get by with a basic welder's helmet that takes welder's glass filters -- the auto-darkening lenses are very expensive.

Do not skimp on the gloves -- you will be working with materials that get VERY hot. Also, you'll need a welder's hammer for arc -- it's used to knock the flux/slag off the weld after it cools.

Anyway, the instructor should be able to supply you with a list of what you need before the first class. Despite the attractive prices of some of this stuff online for your first purchases you should visit a good welding supply shop that works with the trade and don't be afraid to ask questions -- those guys know their stuff. Home Depot, etc. also sell some of the things you'll need but their selection and knowledge of the product aren't that great. You may pay a little more at a welder's supply shop but you don't want to take chances on your equipment -- the safety hazards in welding are very manageable but can be serious if you aren't set up right.

Have fun with it -- It's a great skill to learn!
posted by Opposite George at 11:51 PM on December 18, 2005

Good advice here. I would like to add, if you choose gas welding, use welders goggles even if you feel that you can weld/braze with clear lenses. Eye damage from the UV component of the flame(and the welding arc) is cumulatative. If you go with gas welding, use MAAP or some other fuel gas instead of Acetyline. The fuel gasses are much safer. Go to a welding supply place and stock up on their safety pamphlets. Wear heavy clothing (always have your arms covered) around welding arcs. The UV can go through thin clothing. In the early years I have done arc welding in a thin shirt and found the outlines of what was in my shirt pocket outlined by the burn on my chest. An easy way of developing the close hand/eye coordination that fine welding requires is to do needlepoint or something simular. Have fun
posted by Raybun at 5:35 AM on December 19, 2005

I'm looking to be able to weld bike-type components or general art, household welding.

I'd also recommend a MIG class, based on this information. It's a lot more easy to pickup than arc/stick welding as the gun & trigger provide a fairly intuitive feel and system of control. The equipment will also be more readily available - they have lots of consumer-oriented MIG setups that come with a small cart, a gas cylinder and a spool to get you going.

Arc is great for heavy materials and rugged jobs but is also the most difficult to master. I've taken SMAW Basic through Advanced, the last course being focused on joining structural beams (in dozens of passes, about 3 hours on each joint). These joints are then cut, dyed and x-rayed for defect inspection.

Its advantages outside of penetration and power are the self-contained shielding elements created when the rod is consumed. This is what you often see used to join the initial structure of parking garage staircase, for example. It's impossible to feed all that wire and gas through a cable up there reliably, so stick is your only option. If you're doing really, really heavy artwork (like welding farm equipment together) you'll definitely want to learn this.

To put it in perspective, my girlfriend could barely slap two quarter-inch plates together with Arc her first time around. After about 5 minutes on a MIG, she could "sign" her name with a fairly steady bead.

After you master MIG, you can jump over to TIG which produces the most beautiful and precise joinery. You see a lot of this on headers, frames, etc. It's most similar to MIG (not by much) but is just as difficult to master as Arc, if not more so.

Oxy-Acetylene is very tough to learn and master. My instructor was a veritable god with it though, and would use it quite often with a small shop-built jig to heat and bend various wires for repeated forms (flower loops, letters, etc). It's really quite handy in that respect, but I think most of its functionality has been stripped out by the newer technologies. Of course, if you're out of electricity and you really need to a cut something - having that skill can be priceless. Most guys just reach for the plasma cutter these days though. He described it (and SMAW, to a lesser extent) as "a lost art".
posted by prostyle at 7:31 AM on December 19, 2005

I think you will find that learning to weld bike frames is not a trivial matter. The walls of most bicycle tubing are so thin it is like welding beer cans together. We had to hire welders once for some very thin material and a lot of supposedly experienced guys just couldn't hack it. I am sure that was in large part due to their inexperience with thin materials which they would not admit to us. They probably could have picked it up in a few weeks but we didn't have that luxury. Also, I think most frames are TIG welded these days, but I am sure some Googling could tell you more. I also know that there are frame builders who give frame building classes which include frame geometry, welding, etc.
posted by caddis at 7:49 AM on December 19, 2005

As a former pro with a wallet-full of 6G pressure pipe certifications, I would say that most of the above is reasonably sound advice.

Caddis is right. You may as well forget about bike frames unless you have exceptional hand-eye co-ordination and are ready to devote at least a couple of years to learning the craft. On the other hand, if you just want to whack some stuff together... skip the class, spend your tuition money on a cheap MIG welder and read the manual. Pay close attention to the part about penetration.

Welding is like anything else, in that what you get out of it is directly proportional to what you put into it.
posted by Huplescat at 2:24 PM on December 19, 2005

Response by poster: After reading your suggestions, I think I might rent a Mig welder to give it a try.
posted by drezdn at 7:59 PM on December 20, 2005

Response by poster: And buying one would only be a little more than the cost of a class it seems.
posted by drezdn at 7:59 PM on December 20, 2005

I just now came back to check this thread, and it looks like I owe you an apology for that bit of hyperbole about skipping the class and buying a cheap MIG welder... not a very good idea.

While a good MIG welder vastly simplifies the welding process, I’m certain that a cheap one would drive you crazy. It’s a fairly complex machine and, as such, even the best ones are subject to a multitude of problems. In my experience with first class industrial MIG welders I would guess that I did 20 minutes of machine maintenance for every three hours of welding.

Also, of all the welding processes, MIG is least adept at welding vertical and overhead joints. Unlike TIG or SMAW, MIG only works really well when the work piece is laying flat.

I guess it would be best for you to take that arc welding class.
posted by Huplescat at 4:43 PM on December 30, 2005

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