Tell why I'm doing it wrong!

I always open both Oxy and Acel valves fully to back seat them, why only a 1/4 turn on the Acel?

 

Not to steal Willie's thunder, but it's important to know that unlike most compressed gasses thathave nothing else in the cylinder, Ac tanks have acetone in them to dissolve the Ac under pressure that way they can pack more gas in the tank. If you open the cylinder too far you can force some of the acetone to come out with the Ac which can be dangerous. I once received an exchange cylinder that someone had added more acetone to for some reason (???) when I went to light the torch liquid acetone shot out and the regulator got so cold it immediately iced over! I called the supplier and by the time I had finished questioning his parentage they brought another tank within the hour.

 

Good to know. Thanks.

 

The real important point is that acetylene gas cannot be compressed - beyond approximately 15 PSI, or it will self ignite. Acetylene dissolved in acetone can be put under pressure, so it's used to put the acetylene in the cylinder under pressure. Notice the RED LINE on the acetylene gauge at 15 PSI? It's a real good idea not to exceed it. Also the reason you shouldn't lay the cylinder down. If you are getting acetone out the cylinder it usually means you're trying to pull more acetylene by volume than the tank is capable of furnishing. If that's the case, move up to a bigger tank. (The acetylene has to leave the acetone as the pressure decreases from flow thru the torches, and can only release so fast for a given size cylinder).

 

RMF, is there a reason you don't want to use your MIG welder for sheet metal work? From what little I've tried, welding sheet metal with gas produces a lot of heat, which is likely to warp your panel, cause 'oil-cans', etc. Just a warning, it's not easy. (I was really spoiled in my body shop days using a MIG welder....so maybe I'm a little biased??)

Gary

 

My "MIG" can't be upgraded to run with gas. Effectively it's a flux-core welder. Additionally, the smallest wire it can handle is .030, whereas .024 seems to be reccommended for sheet metal. The young lad has tried welding sheet metal with the .030 flux core and it's really difficult not to blow holes in the metal. He can do it by basically giving it a tiny shot, but it would take forever do cover any distance with a million tiny shots and would likely burn out the controls on the welder....

 

You are still better to weld the sheet metal with the mig IMHO. OAc can certainly be used, but the learning curve is HUGE. If you are determined to learn to gas weld sheet metal, do find a place to take a class or someone who can teach you. Trying to learn on your own is like trying to teach yourself golf expecting to enter the PGA without any instruction.
In the long haul you would be money and time ahead if you sold your small MIG and bought the Hobart (division of Miller) 140 MIG that Northern Tool sells for <500.00. That's the unit I use and it does a great job, uses .025 or .030 wire on std 8# spools, comes with the shielding gas reg, and runs on std. 115V 20A circuit even includes a free cart and shipping.
Spot or stitch welding with your MIG won't hurt it, that's the way you weld sheet metal. If blow thru is a problem, try backing the weld seam with a piece of 1/8" thick copper clamped tight to it. Never try to weld more than 1/4" at a time skipping around the piece until the weld is complete.

 

Ax,

I'll leave it up to the young lad. The last thing I'll do is practice oxy-ace welding on my new dash. He can weld oxy-ace, Mig, etc....

One thing you didn't answer was ;

Can you use solid core MIG wire (like .035) either in a single strand or twisted to double it up with oxy-acetylene? Or am I just getting really stupid here?


Thanks,

 

Yes, you can use the solid mig wire, or the solid wire meant for tig, or, if you're really on a budget and don't need a really strong weld, wire coat hangars! In fact, anything steel you can cut into strips and feed into the weld pool will work, with strength composite with source metal. Only caution is to avoid any welding of anything galvanized, as the fumes are poisonous. Might also point out that one should read up on the various types of flames available when oxy-acet. welding, ie, neutral, oxidising, carbonizing. Each has an effect on the quality of the weld.

 

Yes std Mig wire can be used as filler rod in gas welding, you'll just go thru it pretty quickly compared to 1/16" wire but it will be cheaper.

 

The first gokart (before the name had even been invented) my father and I built in our basement when I was ~ 11 we gas welded together using coathangers for rod. We borrowed the torch and tanks from a neighbor who owned a body shop on the weekend when the shop was closed. We spent the weeknights cutting and fitting parts and would weld all weekend, after a couple weeks my mother would find clothes on the floor of the closet, we had "borrowed" the hangers for a more noble cause! We didn't have much money, so it was built from all scrounged parts and materials, angle iron frame from a bedframe, engine from a gas powered washing machine, wheels from wheelbarrows, etc. but that's a story off topic sorry.

 

Ax,

don't know if that story was off-topic or not, but it's in line with my budget...

 

Ahh, I see the issue. Well, if you're welding on a dash, the curvature will make it much more warp-resistant than if you were welding on a large flat panel, like a door. So that will be much easier.

AX is right, doing little tiny spot welds shouldn't hurt your welder, I've done that for hours straight welding on new roof skins, door skins, etc. Each bead is about 1/8" long, very minimal heat produced but the weld flows out and penetrates just fine if you get the welder adjusted just right. I also used to hold the welder in my right hand, and a blow-tip in my left used to cool the local metal down right after I let up on the trigger of the MIG. That really works well on a tough panel weld....

 

The air hose is a neat idea. I never thought of that....

My neighbour has a little pi__-a__ air compressor that isn't much good for anything, but it would certainly handle repeated wee blasts every 30 seconds/minute or so. Cool!

Hey ***** - make sure you mention that air hose thing!

 

Yeah, it doesn't take much of a compressor to cool some small welds, just make sure the pressure is up so you get a lot of volume. You'll be surprised at how fast it cools the panel down. Another thing, try to blow a little more parrallel to the surface, rather than straight at the panel. I you run a lot of air pressure you can actually bend the sheet metal inward a tiny bit if you blow directly at the sheet-metal. We used to use that trick to 'shrink' stretched metal, we'd heat up a large area about 5" in diameter, get it red hot, then hit it with a direct blast of air for 5 seconds, it would shrink the metal down and push it in.....but there's a knack to getting it right.