gas or not?

Hello everyone, I'm in the market for an oxy-acetylene welding/cutting set but I have a few questions before I make my purchase. I have done some stick welding before but never used gas so I'm a little nervous about the safety aspects. I want the set for making sculptures out of scrap metal parts and I wanted the most flexible tools I could get. My questions:

  1. What can't I do with oxy-acetylene? Or, is there something of comparable cost that would be better for me to use?
  2. I'm going to have the tanks in my garage at home, which is about 25 feet from my house and my neighbour's. Is this legal, are there any regulations about residential areas I should know about?
  3. What is the best reverse-flow & flashback configuration ( at the torch or tank or both)?
  4. The Smith booklet takes about '4 preheats' on a tip, what does it mean?
  5. My garage is unheated, would this be a problem in winter when everything freezes?

Thanks very much in advance for your help. Adriaan

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Depends a lot on your skill and patience. Try to find someone who can give you hands-on training. As much as I like to self-teach myself, welding is one field where a little hands-on help goes a long way.

Your ideal setup would be a MIG, a TIG, and a plasma cutter. Since that would set you back about $4000-$5000 for new gear, I suspect it's not an option.

My biggest problem with O/A is that it takes awhile to heat the material to welding temp and that causes too much warp and discoloration. My next new toy will be a TIG.

For a beginner at least, O/A will limit you to steel.

Thousands of O/A sets in garages throughout the world.

When I'm done I always: close the bottle valves, bleed off the pressure in the hoses one at a time, turn the regulator pressure adjustments CCW until they go slack, close the torch valves. Just like Mr. Cole taught me in HS shop class 35 years ago.

I probably should leak-test the acetylene regulator connection to the bottle each time I put it on.

I don't use them. See your dealer if no one else replies.

Sounds like a cutting torch (or gas axe as we call them). Cutting torches have multple O/A flames positioned around a central oxygen jet. You use the O/A flames to get the metal up to welding temperature then turn on the oxygen. The oxygen will then burn through the metal. Works well with steel, works poorly with cast iron, and not at all with everything else.

I've seen guys thawing pipes with O/A rigs so they must work ok in the cold.

Reply to
Jim Stewart

Joe wrote: (clip) I want the set for making sculptures out of scrap metal parts and I wanted the most flexible tools I could get(clip) ^^^^^^^^^^^^ That would be oxy/acetylene. You can weld, you can braze, you can silver solder. You can cut and you can heat metal for forging and bending. There are lots of other tools that are very good for particular applications, but none of them completely replaces the O/A torch.

Reply to
Leo Lichtman

I have a Uniweld on my service van. The only time I ever had a problem was when the plastic trigger guard on the fire extinguisher broke and I didn't notice it, and I picked up the torch tote and managed to fire off the extinguisher. White powder went _everywhere_.

I do know that Uniweld at least has optional back-flow preventers/flame guards which are fitted to the hoses at the torch handle. Cheap, and work well. Cheers, Fred McClellan the dash plumber at mindspring dot com

Reply to
Fred McClellan

The thing you can't do with O/A, at least you can't do it well, is to cut non-ferrous materials. A plasma will cut anything conductive, but O/A works by using a jet of oxygen to burn iron that's been preheated to ignition temperature. That won't work cleanly with other metals (doesn't even work with cast iron).

You can weld most anything weldable with O/A, though it is sometimes difficult, and always slow. You can also braze and heat.

Don't know where you're located, but there aren't any regulations against it where I live.

The main reason for using these is to prevent fire in the acetylene hose due to oxygen back flow into the acetylene hose if the torch tip becomes blocked. So the best place for the check valve is where the acetylene hose connects to the torch. The checks normally come in pairs, so you can put one on the oxygen side too, but the likelihood that acetylene pressures would become so large that back flow could occur into the oxygen hose is slight.

Cutting tips have multiple preheat flames which surround the central oxygen cutting jet. Their purpose is to heat the metal to kindling temperature so the oxygen jet can then cut steel by burning. Welding tips will have only a single flame cone (excess oxygen is a no no when welding). Rosebud tips also have multiple flame cones, rosebuds are used for heating.

No. Acetylene sublimes from solid to gas at -84 C. It is what's called a "reluctant" liquid in that you'll never normally find it in the liquid state. Normally, the acetylene is dissolved in acetone in the tank. Acetone freezes at -94.7 C. Oxygen liquifies at an even lower temperature. So unless you live in an *extremely* cold part of the world, you needn't worry about this.


Reply to
Gary Coffman


I learned to gas weld (oxy-acetylene) waaaay back in high school, and every time I have wanted to do something with metals, I invariably end up looking at gas welding first. It is probably the most versatile metal modification system you can own. Welding, Brazing, Soldering and Cutting (ala the old "gas axe" approach) can't be beat for the money in any other system I can think of, and I own a fairly decent assortment of tools, including a metal mill and lathe, several cutting/welding systems, and a host of air and electric metal and woodworking tools as well

With an OA setup, you can cut iron and steel (a 4-preheat tip is essentially a cutting tip, my current one is a 6-preheat tip, meaning it has 6 preheat jets surrounding the single cutting jet of the cutting head tip. A 4-preheat tip sounds to me like a fairly small system.)

You can weld iron and steel in thinner gauges, but can't do a decent job of welding thick sections without a lot of practice and very large tips, so I resort to Stick Arc welding (the second type I learned) and which is pretty inexpensive because you don't have to buy or lease tanks. Third is MIG welding, but the current MIG I own is set up for flux cored wire so I can't do very thick sections with it. Though I have the tank for separate gas and solid wire, I've not taken the time to get the tank filled because Aluminum and Stainless require different gasses, and I don't have any projects on my current list that actually _require_ me to use stainless or Aluminum, particularly in the relatively thin sections my inexpensive MIG system could handle. (MIG and TIG systems for thick metal sections are very pricey compared to similar thicknesses in Iron and Steel using OA and Stick AC or DC arc welding.)

With an OA gas welding setup, you can also braze a wider variety of metals, Silver Solder, or even solder using standard tin-lead or lead-free solders if you wish. The only thing to keep in mind is that the flame of most tips is usually pretty intense and not spread out like a propane torch, so if you are going to be soft soldering (tin-lead or lead-free solders for plumbing) you will want to be moving the flame around a lot to spread the heat or you could burn through the base metal. If you do a lot of cutting, sometimes OP (Oxy-Propane) may make sense, but it generally isn't as hot and requires different tips than OA, and I can't recall anyone actually doing much welding with an OP setup, just demolition or other cutting....

Learning to gas weld is an art, and like most arts, it is easier if someone can teach you, or at least watch while you are in the earlier stages. Once you have the basics, you can pretty much go on your own. Trying to learn from a book or video is usually pretty frustrating, but having someone that is a good welder (or good welding teacher) can get you into decent territory in a couple of hours. It doesn't take a long time to learn, so having someone else stand by while you get the basics usually isn't too long or even that expensive if you have to pay someone to teach you. A night class or community college extension course could be really helpful because they tend to also bring up a lot of other subjects and expand your horizons a bit... (like AC Arc (stick) welding and other metal fabrication skills. ... but I digress ....

To directly answer your questions:

1) nothing can really touch the versatility of gas welding, and it is pretty inexpensive overall. If you buy/lease larger tanks, your gas costs per job will be considerably less than if you get smaller tanks. If you are refilling your tanks in six months or so, you probably have big enough tanks for your typical use. If you don't go through all the gas in a set of tanks within a year, you probably have a tank set too big for your typical use. However, if you are going down for a refill every month or two, you might think about upgrading to a bigger tank size. Generally speaking, the bigger tank size, the less per cubic foot you pay for the gasses. If you do a lot of cutting, get the next bigger size Oxy tank. If you mostly do straight welding/brazing and such, get tanks of similar physical (dimensional) size. Cutting takes a lot of extra oxygen compared to regular welding/brazing/heating, so if you do a lot of cutting, you will be running down for Oxy refills a lot more often than Acetylene. Typically, if you start with the standard paired sizes, you can watch and decide what to do later, particularly if you lease tanks. If you do buy your own tanks be aware that many suppliers now charge an exchange fee when you refill them, because tanks have a finite life span, and someone has to pay for the obsolescence of old tanks. You can either pay it in the gas cost, or directly in a fee per refill/exchange. By the way, most places will exchange tanks when you go in for a refill. They don't actually refill _your_ tank when you come in, but give you another tank that is a "lease" or a "owner" tank. If you don't do much welding or cutting, you can end up with a tank that is near it's re-certification time, and if you're not watching, you might end up with a higher refill/recertification charge than you expect. (It has happened to me, even though I bought new tanks, refilled them once, and got caught because the hydro-test expired on the tanks I had at my home at the time. Many vendors keep decent track, but some don't and you might end up getting charged more than you might expect. As a result of past problems with this, I currently lease the tanks I now use, and the supplier/owner takes care of obsolescence. It costs a bit more than owning tanks, but I don't have any unpleasant surprises when I refill..

2) Most places pressure tanks aren't heavily regulated. The Acetylene tank is actually full of a filler (like balsa wood) that helps keep the acetylene stable at high pressures inside the tank. When you are using Acetylene, keep your pressures in the 7 to 12 pound range for most uses. (Avoid higher pressures, Acetylene becomes dangerous above 15 PSI, which is why an Acetylene gauge is red above that pressure. Oxygen is typically more dangerous, especially if you don't realize that a bit of grease on the threads or mating surfaces of an oxygen regulator could cause a very nasty fire or explosion. (If you are cutting something with an Oxy-Acetylene torch that has oil or grease, don't try to "blow it out" using the oxy jet. It'll only get much worse. DAMHIKT ) Of course in some areas, nearly everything is illegal that you'd want to do except sleep, so your mileage and local regulations may vary. However, I'd hazard a guess that even in the inner city, there is at least one Oxy-Acetlyene rig for every 10 or 20 homes, certainly a lot more in the suburbs, no matter how close the homes are. You are more likely to have problems from setting something on fire from other causes than from the inherent danger of the high pressure gasses. Of course, you should always observe proper fire safety, and be aware that making something hot with a torch may cause other things to catch fire, and be ready for the consequences. If you have gas heat or a gas hot water heater, be particularly careful that you don't have any Acetylene leaks, because the pilot can start a larger fire if the Acetylene is leaking. However, you will definitely smell Acetylene before it gets anywhere near a concentration that could cause an explosion from such an ignition source.... If in doubt, take the safe approach and keep the tanks away from any ignition sources.

3) Reverse-Flow and Flashback protection is pretty much up to the individual, but I prefer a set of flashback valves just before the torch handle. That way, I don't have to worry about the additional capacity of the hose set, or of destroying a hose set during a big flashback. That said, I've never had a flashback that was more than a small pop in the actual tip, but then I'm pretty careful and have been using Oxy-Acetylene rigs on and off for something around 35 years... Even so, I wouldn't use a rig without a flashback arrestor somewhere in the system. They are cheap insurance, IMHO.

4) Preheats are the number of fuel gas holes (jets) on the cutting head. Most larger capacity systems have 6 preheats, and some have 8 or more. 6 seems to be the most popular of the rigs I've used over the years. The preheats get the Fuel/Oxy mix and are used (as you might expect) to preheat the metal to prepare it for cutting with the oxygen jet. The central hole is usually larger and puts pure Oxygen through the tip, which will actually burn the iron or steel, and blow slag (unburned metal) out of the cut. If I were buying another torch, I'd tend towards 6 Preheats because you can typically cut thicker steel with one, and you can typically get smaller tips for the big torches, but not usually big tips for the small torches. Bear in mind that if you are cutting much at all, you will use a lot of Oxygen, and the torch will get pretty hot. A smaller, shorter, lighter torch will get the handle hotter much quicker than a larger system will, however, the heavier handle of a heavy duty torch set will be more tiresome if you only do small, detail work. You will need to decide what kind of work you want to do before you purchase a torch set. Of course, if you have the extra cash, a big, heavy duty set and a small, lightweight torch, each on it's own hose set with a siamese (Wye) setup is sort of best both worlds...

5) Where I live, it wouldn't be any problem at all, because the lowest temperature I've ever seen here in the middle of the winter is about 59 degrees.... Of course, I live near sea level in Hawaii, and your temperatures probably vary a bit more than mine. When I lived on the mainland, I have used Oxy/Fuel rigs in temperatures down to about 10 degrees F, though Acetylene tends to do better at lower temperatures than Propane, unless about all you are doing is thawing pipes... You can probably do ok at pretty low temperatures, but you will have to allow more time for preheating if you are cutting iron or steel, and regular welding, brazing and soldering processes will take longer in cold temperatures. There are probably an incredible number of OA rigs in garages across the US, many of which don't get used very often. If you are a tinkerer or artist, you are likely to use them more than the occasional use "just in case" mechanic type. Since I've moved to Hawaii, my costs for cylinder lease have been much higher each year than the cost of the gasses. (sigh) I guess I've moved to other things (though I do spend more for stick welding rods.... Even so, I wouldn't give up either of the OA rigs I have in my workshop, though I may drop back to smaller tanks soon if I don't get more cutting/gas welding projects in my hopper soon...

There was something else I wanted to say, but the ol' brain just went in to neutral, so I'm going to close....

Take care, learn how to weld properly, always weld or cut on a fireproof surface, and enjoy yourself. If you do much iron/steel welding, get an arc (stick) welder next, then if you have the extra money, maybe a MIG or TIG rig. Given a limited budget, you can do a lot with no more than an Oxy-Acetylene rig for welding thin sections (to perhaps an eighth of an inch, pushing it to maybe a quarter of an inch occasionally unless you have a really heavy duty rig), Cutting to about an inch or so depending on your rig capacity, and with a relatively inexpensive AC Arc Welding (stick welding) rig, you can weld up to about an inch thick without too much trouble. For many years, that was about all anyone used anyway. DC arc welding helps for control and overhead welding, and MIG and TIG are good for welding thin sections and other metals (such as stainless steel and aluminum), however, getting an real capacity for welding Stainless and Aluminum thick sections costs an arm and a leg, and probably another arm, depending upon where you live.

Good Luck, Stay Safe, and enjoy yourself!

--Rick AH7H

Joe wrote:

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Hmm. Extremely non-polar molecule. No vanderwalls forces I guess.

Ever make ethanol ice cubes? :)


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Reply to
jim rozen

Even at 300PSI?


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Reply to
Tim Williams

Acetylene has a critical pressure (905 PSI), at least theoretically. But as you know, acetylene is very unstable at high pressures (that's why it is stored dissolved in acetone in cylinders). So the critical pressure is never reached in practice.


Reply to
Gary Coffman

Can you cut aluminium?

I suspect trying to cut magnesium would be a bad idea.

Reply to
Ian Stirling

Can you say "fwooOOOOFFF"? LOL!


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Reply to
Tim Williams

Not the way you'd cut steel. Hitting the oxygen lever just makes a godawful mess (aluminum oxide has a *much* higher melting point than pure aluminum). You can melt through it with a welding tip, and since aluminum is hot short, it can be convinced to drop out, but the cut will be ugly and very ragged.


Reply to
Gary Coffman

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