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Need help learning to cut with Oxy&Gas

Discussion in 'The Hokey Ass Message Board' started by Tugmaster, Aug 30, 2013.

  1. So I'm trying to teach myself to cut using oxy acetelyne and I'm having some issues. I'm working with some 3/16 steel. My torch is set up with a size 0 tip and I'm running 25 lbs of 02 and 5 lbs of gas. When I make a cut the molten metal keeps weeping back in and filling in where I just cut. I'm getting a little frustrated and thought I would seek some advice here. I'm also using "A" size hose with adapters to be able to use a torch with "B" size fittings, if that matters..
    I'm thinking I might want to use a smaller 00 or 000 size tip but I'm not sure.
    Any suggestions?
  2. Tip size makes a big difference. Manufacturers will give the cutting range of tips ('up to 1/2" thick' for example), get a tip where the maximum thickness it's rated for is as close to the steel being cut without going under.
  3. saltflats
    Joined: Aug 14, 2007
    Posts: 10,599

    from Missouri

    Try differant speed and point the tourch (slite angle) in the driction you are moving.
  4. My torch is a older Hi-Lite. It uses the same tips as a Harris. I found a guide on line. It says the 000 tip is for sheet metal up to 3/16".
    I think I'm gonna get my hands on one of those before I proceed any farther. If I'm not using the correct tip I'm thinking everything else may be in vain. Todd

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  5. 1967gt
    Joined: May 27, 2013
    Posts: 400

    from ohio

    That shit is not a toy !!! Its a bomb in a cyl. Get it ? Just my O...
  6. Thanks, I never would have known that!

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  7. Well, there you have it. Irrefutable proof of impending doom. Everyone get rid of your oxy/acetylene rigs and go hide under the bed.
    BTW, my old welding instructor used to go nuts when someone said "oxygen and gas or, worse yet, "air and gas" He'd say that either one is "air" and they're both "gas";)
  8. Ole don
    Joined: Dec 16, 2005
    Posts: 2,915

    Ole don

    Well, to prevent the bomb effect, always use the cylinders upright. If the acetylene is layed down, the white stuff comes out of the tank and plugs the tips. If you EVER see white stuff comming out the tip, shut it all down and return the short tank. They will give you a new one free. The tank needs a filler inside. If the tank had nothing inside except acetylene, it WOULD be a bomb. Your problem; try laying the tip back, up to a 45 degree angle. Hold it close enough so the fire tip is near the work, about 1/4 inch up. Squeeze the handle and hold it all the way tight, so the full volume of air will push the molten metal away. A good straight line held with both hands may leave a good amount of slag on the bottom, but a rap with a hammer and the two pieces will part. Very little grinder work will be needed. Practice, practice, practice.
  9. I have a salvage business, and use a torch EVERY day , Experimentation / use is the only way you will become proficient , I would up your Acet pressure a bit , And when lighting and adjusting your mix , Light the acet , turn it up till the flame seperates from the tip , then turn it back down til it (the flame ) returns to the tip . now add the oxy til you see the six little blue cones about 1/4 inch from tip, snd clean. Now hit the enrichment/ cut handle , The cones should stay in the same place , if not , a bit more oxy should be added, NOW HERES WHAT I DO ,,, I add a bit more act, so it makes a slightly more hiss , but , does not seperate the flame from the tip. add a bit more oxy, and get the cones uniform again, then start cutting ,
    Only experience will get you better at this , find some scrap and play with different thicknesses ,mixes , etc. I ADD A LITTLE MORE GASSES TO MAKE A HOTTER , CLEANER , CUT. I've cut 5/8 inch with a 000 , and 1/8 with a 0 and vice versa. just by speed , mix change . Joe
  10. B Ramsey
    Joined: Mar 29, 2009
    Posts: 643

    B Ramsey

    posts like this in just about every thread (seems like) are really fucking annoying.
  11. I think we have a runner
  12. hooliganshotrods
    Joined: Dec 2, 2010
    Posts: 607

    from Calgary

    I'll throw my two bits in. I teach welding for a living. My first thought is that I am surprised that NO-ONE has mentioned anything about the torch settings. I'm not talking about the pressures at the bottles, I'm talking about where you are setting the flame up with regards to the smoke range.

    First off, your tip size is fine at 0, a 00 would be nicer but it's not essential. Your bottle pressures are in the ball park for sure, I usually run 3psi Acetylene, and 30psi O2. The MOST important thing is how you set up the acetylene PRIOR to adding oxygen. When CUTTING you want a lot of black smoke (carbon) in the flame, you'll see it floating around. If you set your torch and take all the black smoke away before adding oxygen you are at the top of the limit and may explain why you are melting the pieces together rather than cutting them apart. When you dis-spell the black smoke you are increasing the available volume of heat, it's not changing the output btu's of the flame but giving you much more volume quicker. More volume of heat means things heat up quicker in a pre-determined area. For a 0 tip (or any tip) to get you close, light the acetylene, turn the dial until the black smoke goes away and then back the valve down a full turn back into the smoke range, then add your oxygen and make a neutral flame. (A flame where the blue cone and feather just meet and no further or you will oxidize the flame making it hotter)

    Once you have adjusted the torch in the smoke range and adding oxygen do not start turning the needle valves, by doing this you won't know where you are with regards to the Acetylene.

    A good rule for thumb for setting the Acetylene in the smoke range is that once you add oxygen, if the torch pops or backfires then the Acetylene is set too low (too much smoke) The torch will back fire because it can't combust the fuels properly, acytlene needs to burn at 17-25ft per second, anything less will result in a backfire, burnback or god forbid a flash back.

    Another thing to consider if your torch is set up properly in the smoke range for cutting is:
    1- is the tip clean
    2- direction of travel with the torch, backhand or forehand.

    For 3/16" material, you should have the torch tilted in the direction of travel...."forehand" and gauge your travel speed by looking at the kerf as you cut. If the torch is set right it shouldn't stick together, increase the travel speed across the cut and see if it makes a difference.

    Also, it is VERY smart to install flashback arrestors at your bottles to keep you safe.

    It is worth mentioning that for gas welding with C2H2/O2 you would need to balance the tip/torch so that equal parts of gas and oxygen are mixing. You would also be OUT of the smoke range for welding applications.

    Hope this helps.
  13. Wild Turkey
    Joined: Oct 17, 2005
    Posts: 902

    Wild Turkey

    Try something thinner and see what happens -- you'll see what difference thickness makes.

    Also be aware that some steel is not "homogenized" and you'll hit patches that will pop and blow your flame out or not cut like the rest due to inclusions.

    It's especially bad in thin stuff -- I was cutting on some shipping containers and got a plasma cutter that would go right through those spots.

    And print out what hooliganshotrods said. Make several copies and post where you'll see them. He makes a lot of sense and will save you lots of time.
  14. 42merc
    Joined: Dec 19, 2010
    Posts: 750


    Tugmaster, take Joe's Garage advice. He's spot on.
  15. It is just a guess, but I think you might be running a little rich on acetylene, that will give you an extra frothy slag on the back side.
    I use LP gas rather than acetylene so the comments on flame set-up are very different from what I do.
  16. Joe,

    Just went to the garage and tried it again per your directions. I can't seen to get the flame to separate from the tip on the acet. As a matter of fact I can't turn it up high enough with acet only to get the soot to go away. I turned the acet up to 12psi still no change. I am beginning to wonder if the "A" size hose is to restrictive. Todd
    Last edited: Aug 30, 2013
  17. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,910


    I have been dead a few times. Wasn't that bad.
  18. Todd, do you have a high school or JC close that has a fabrication or welding class? If you happened by there and introduced yourself and asked for some guidance I'm betting the instructor would be glad to show you the correct technique. Also, it's really important that the tip is clean, use your tip cleaner to get the holes as clean as you can before you start. Usually when it's clean it kind of makes a crackling noise when you hit the lever.
  19. sport fury
    Joined: Jul 25, 2009
    Posts: 593

    sport fury

    a cheaper way to cut and heat is to use propane and oxygen. it burns to dirty to weld with but it cuts and heats well.
  20. pila38
    Joined: Mar 25, 2009
    Posts: 763


    Good info thread...except for the bomb talk.

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  21. d2_willys
    Joined: Sep 8, 2007
    Posts: 4,148

    from Kansas

    I set the cutting torch to 15psi O2 and 7psi acetelyne. I was tought to adjust the acetelyne to get a decent flame with black smoke, then with the main oxygen opened all the way, adjust the cutting torch valve till the flame is a nice blue conical flame with no blue fog around it. Then heat the metal till red and with the nozzle pointing slightly in the cutting direction, depress the cutting lever and cut.
  22. Learning to cut metal with a torch is like .................."how do you get to Carnegie Hall"...................PRACTICE, PRACTICE, PARCTICE
  23. I do all my OA cutting with a cutting head only. Get the flame right, similar to a brazing cone but hotter, then hit the oxygen handle. Any time I did cutting with a regular tip, it clogged up quickly.

  24. saltflats
    Joined: Aug 14, 2007
    Posts: 10,599

    from Missouri

    I guess you know all the safety rules or you would have asked. Lord I hope so.

    I was learned to never have the flame leave the tip when adjusting.
  25. Keep
    Joined: May 10, 2008
    Posts: 662


  26. Acetylene can become unstable over 15 PSI, there is acetone and asbestos fiber in the cylinder to keep the acetylene from exploding, but not in the hoses.
    Do not go above 15 PSI on the gauge!
  27. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,910


    More likely diatomaceous earth, than asbestos, if the tank was made after 1985.
  28. stimpy
    Joined: Apr 16, 2006
    Posts: 3,547


    and also make sure the Oxygen valve at the bottom of the candle stick is open all the way , I seen guys try to cut and not get full pressure to the tip because the valve at the bottom was partially shut , open the o2 valve on the bottom to full open and adjust the fuel with the other knob like normal , use the valve on the head to adjust the cutting flame oxygen needs , and always 1/4 to 1 full turn on the fuel tank . and wide open on the oxygen tank and leave the key in the top of the fuel tank till your done . and do not use a allsize wrench on the acetylene tank valve , buy the real one in a emergency it will make it easy to shut off .

    as for fuel you use more propane as it lower in BTUs than acetylene , and propleyene is just a little cooler than ace , but cheaper and easier to find since the carbide plant let go several years ago .
  29. I wonder if you have enough pressure in acet bottle , or your regulator is restricting ?????You should be able to make the acet blow out of there like a blow torch , and separate the yellow flame better than an inch from the tip. then turn the pressure back down ,
  30. hotrodarchaeologist
    Joined: Dec 4, 2007
    Posts: 497

    from Maine

    "Also, it is VERY smart to install flashback arrestors at your bottles to keep you safe."

    Would you, or someone else be able to recommend a good quality set of arrestors? Install at torch or at regulators, or both for added safety?

    Great thread as I am a self taught OA torch user, and I have learned a lot...thanks!

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