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  1. #1
    Bill D is online now Titanium
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    Default Air-Acetylene vs propane torch

    I have never used one so how does a Air-Acetylene torch(like a prestolite) compare to a propane torch for silver soldering etc. How long wil it run on a small tank. Can you weld steel with it or do you have to have a oxygen torch for that?
    Bill D.

    http://products.esabna.com/index.php...jet_outfit.pdf

  2. #2
    L Vanice is online now Diamond
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    I began using a Bernzomatic propane torch around 1955, and that is what I used for silver brazing and bullet casting for about ten years. Then I got my first Prest-o-lite outfit. I was glad to have the flexibility of five different size tips. And the gas cost of a B tank seemed much lower than a pile of throwaway propane tanks. The B tank is about knee high. I don't know the exact cost difference at present. The last time I traded B tanks, I found my usual supplier had sharply raised their prices, so I called another welding gas company and found they were much lower. So it pays to shop around. I also have some of the little MC tanks, but they are not as economical. The MC tank is not much bigger than the Bernzomatic tanks. I only use one when I have to use a torch away from my welding area. These torches will not weld steel. By the way, these B and MC tanks were originally used to fuel headlamps on cars and motorcycles, beginning in 1904. They made night driving safer. Can you guess why the little ones were called MC tanks?

    I have three sizes of oxy-acetylene torches. A Tescom Little Torch with watch jewels forming the orifices in the tips is perfect for jewelry repair and micro welding. An aircraft size torch for small, not tiny, jobs, and a full size torch for big jobs and cutting. Oxy-acetylene can weld steel and cast iron and also can do brazing. Depending on the torch and tip size, the hotter flame will speed up the brazing process at the risk of getting the metal too hot. I use a B tank of acetylene with my oxy-acetylene torches. They are a lot easier to carry around than the bigger acetylene tanks most pro welders use. The general rule is, the larger the tank, the cheaper the gas.

    Larry

  3. #3
    Mcgyver is online now Titanium
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    Acetylene burns hotter than propane (in air), 2600 vs 2000F. Google and you'll find all the info you need on burning temps....here i did it for you
    Flame temperatures

    I have O/A and propane/air. My propane is not a throw away unit, but a proper torch with interchangeable tips, regulator on a 20 lb bottle like you'd put on the bbq. Cheap and easy to fill - around here welding supply is 9-5 weekdays whereas propane is 24/7 at the gas station.

    For silver soldering small pieces, i prefer propane as there is little risk of getting things too hot (burning the flux) which will happen with O/A unless you heat indirectly.

  4. #4
    jimboggs is offline Stainless
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    A correction, if I may. Oxy-propane can and will weld. Propane or even MAPP, on their own, will not (or even braze well for that matter). I ran my oxy-acetylene set-up on propane for about the first year until I could afford the B-tank. I ran on propane tanks for years doing plumbing as it was much more widely available then here in the mid-west. I have been happy to discover that most local Farm Fleet type stores are now carrying acetylene tanks and exchanges. I got a lot of flack running with a 20lb BBQ tank when I first went out to New England as the old school guys all ran acetylene. The other benefit to my set-up was being able to simply take off the torch handle and hook up directly to my lead-pot. My 20lb'er was good for a couple of months of heavy use (I was soldering in at least a house a week including hot water baseboard). A B-tank will last about two weeks with heavy use, and less with an oxy set-up. I now have a acetylene set-up for soldering and I will confess that I like the characteristics of the acetylene better.

    Jim

  5. #5
    richard newman is online now Stainless
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    Glad to see this posted, I've been wondering the same thing. I've started making banjo hardware and have to braze 12" diameter rings rolled up from 3/16 x 5/8 brass (butt joints)

    I started with a propane turbotorch , but it I felt I needed more heat, so I've been using the turbo torch with MAPP gas cylinders. Seems to work ok, but wondering if I would be better with acetylene, maybe a prest-o-lite type setup like in the OP's link. The small MAPP cylinders are pricey!

    One important question - is their any difference in the toxicity of the fumes from the different gases.

    Also, does one of the fuels provide a superior "brazing environment" for silver brazing?

    Thanks,
    Richard

  6. #6
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    bosleyjr is online now Diamond
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    Quote Originally Posted by richard newman View Post
    One important question - is their any difference in the toxicity of the fumes from the different gases.
    Not inherently. Acetylene, natural gas (ethane and methane, mostly), MAPP (Methacetylene and propadiene) are all hydrocarbons, and when you burn them with oxygen you get carbon dioxide and water as combustion products. If you use pure oxygen, the flame products are entirely CO2 and H2O. If you burn these with air, you get CO2 and H20, but end up heating a bunch of nitrogen in the air, which is why the temperature ends up lower.

    Higher temps for O/A might cause your base metals or fluxes to react. Don't know. But the fundamental products of burning any of these gases are CO2, Water, and heat.

    J

  7. #7
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    9100 is offline Diamond
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    We silver brazed contacts for locomotive braking switches and reversers daily for 20+ years before GE reorganized and closed the shop we dealt with. We were happiest with natural gas- oxygen. We had a "high pressure" gas line installed, but the 2 PSI was marginal for our torches, so we eventually went to propane. We were spending $300 / month for oxygen, so we got an oxygen generator that extracted it from air. I looked at getting a natural gas booster, but the market became so unreliable that we never got to that point. In the beginning, we just used a regular oxyacetylene welding outfit, but that required care to stay between the melting points of the silver solder and the silver contacts we were attaching to copper blocks and the acetylene cost was high. I used MECO torches until I got tired of being burned by the leaky joints catching fire, then changed to Smith and never looked back. I have a Prestolite torch with only one tip, but it is so wimpy that about all I use it for is heating vacuum lines to outgas them. I also have a Little Torch like Larry's, which is a really neat unit, the way to go for tiny work.

    Remember that air is 4/5 nitrogen, which doesn't burn. A gas air torch is blowing one part heating flame and 4 parts cooling nitrogen on the part. About all I use a Bernzomatic torch for is soldering copper plumbing.

    For low volume silver brazing, my vote goes to oxygen-propane and for welding and brass brazing, oxyacetylene.

    Bill

  8. #8
    PeteM is online now Diamond
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    I've got and use:
    - a propane torch with push button ignition
    - an air acetylene torch
    - oxy-propane and oxy-acetylene torches

    The propane torch gets used for quickly heating up things at the bench. It's handy and eminently portable.

    Air acetylene is great for soldering and brazing; and sits at the same bench.

    Oxy acetylene is better for high silver brazing. The air acetylene just doesn't put out enough heat in my experience for either quick work or larger parts. I rarely use it for welding (arc, MIG, wish I was better at TIG, instead for me)

    Oxy propane is great for heating sections to be bent and cutting. At least that's what I use it for.

    If you get a B acetylene tank you could consider adding the oxygen later if your brazing needs require higher heat.

  9. #9
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    tomwalz is offline Stainless
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    Nice timing. I just finished this article on brazing gases Friday.

    Brazing with Gases

    For more on brazing see:
    Brazing Index Addressing Topics like How to Braze, Brazing Tungsten Carbide, Brazing Flux, and Brazing with Brazing Alloy or Silver Solder.

    Happy Easter.

    Tom

  10. #10
    Jim S. is offline Hot Rolled
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    Quote Originally Posted by richard newman View Post
    Also, does one of the fuels provide a superior "brazing environment" for silver brazing?

    Thanks,
    Richard
    One gas I have not seen mentioned in this thread is propylene, a by-product of plastic manufacturing. At work we use a lot of propylene-oxygen for hand torch brazing copper, brass and steel with silver and phosphor based brazing alloy in the mfgr of large HVAC coils. It is an ideal fuel gas because, although the primary flame temp is a few degrees cooler than oxy-acet, the secondary flame is much hotter, making for a much more even brazing flame. It also seems ot go an a very long way and is very easy to store and handle.

    That said, I don't know how easy it is to get in smaller cylinders at the retail level.

    Jim

  11. #11
    wippin' boy is offline Diamond
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    air acetylene kicks ass
    i've used it for years
    with my big tip i can solder inch and a 1/4 copper pipe outside in a wind storm
    the only reason i don't use it more indoors is because the O/A is sitting closer to the bench

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