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  1. #1

    Default Cutting torch questions

    Used to do all of my cutting around here with the stick welder and portaband. Just got a used torch setup and have a few questions. Everything I read on the internet about the basics says when I start it I should have a 10" flam or the smoke in the acetylene should stop. If I adjust it untill the smoke stops I have about a 14-16" flame. I'm not sure what nozzle is on it. It has one center hole and 4 outer holes. I can't read the writing on it. I do have an assortment of nozzles. Should I have a large cone in the middle after I add oxygen, or should i have 4 (because of the 4 outer holes) small cones that don't change when I hit the lever? I can get it to cut, just fills up the cut behind the torch as I am cutting. (moving fast as I can). Also a few questions about safety, the torch and guages are an Airco, and there are no flashback arresters. Big deal? And whenever I shut the torch off (oxy first) I get a flashback or "pop". Should I be doing something different? Thanks fellas

  2. #2
    Gold Member Buckgnarly's Avatar
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    Default Re: Cutting torch questions

    FLASHBACKS ARE A MUST!!! Get them before going any further. I always light the actylene, then add O2 until I get a neutral flame (blue jets coming from all the holes around the center hole).

    Your outer holes are the heating element (acetylene and O2) with the center being the O2 for cutting. An oxy-acetylene simply oxidizes the steel in a VERY rapid manner. You can shut off the fuel (acetylene) and still cut with the O2 as long as you go at the right spped.

    Tip size will determine pressures and thickness that you can cut. It sounds like the kerf is being filled as you cut, which means you are going to fast or the pressures are wrong...or the tip is the wrong size. Look on Smith, Lincoln, Harris, or other good company's website and I'm sure you will find a tutorial on oxy-acetylene cutting. Read that, then come back with questions!

  3. #3

    Default Re: Cutting torch questions

    I take it flashbacks weren't always used though correct? What are the hazards if I do not have them? I guess my main concern is if I am using too much acetylene and what size my current nozzle is as well.

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    Elite Member Shield Arc's Avatar
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    Default Re: Cutting torch questions

    As with welding, and cutting I listen to what is happening. Every torch has a sweet spot, sometimes you only need to press the oxygen lever an 1/8-inch, sometimes a 1/4-inch, what you want is for the cutting cone to sound like a small jet engine.
    First picture is what I like the cutting cone to look like. Second is a neutral flame.
    Attached Thumbnails Attached Thumbnails -cutting-cone-jpg   -neutral-flame-jpg   -flashback2-jpg  


    Miller Dynasty 300.
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    Elite Member Shield Arc's Avatar
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    Default Re: Cutting torch questions

    Here is a good chart.

    Hooper Welding Supply - Tip Charts


    Miller Dynasty 300.
    Lincoln V350-Pro w/pulse.
    Lincoln LF-72 wire feeder.
    Lincoln SG Spool gun.

    Lincoln LN-25.
    1937 IdealArc-300.
    Everlast PowerArc 200.
    Everlast PowerArc 300.
    5 Lincoln SA-200s.
    1800 Ellis saw.
    Hypertherm Powermax 1250, CNC table.
    PROFAX Welding Positioner.
    JD2 model 3.

  6. #6
    Gold Member Buckgnarly's Avatar
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    Default Re: Cutting torch questions

    Quote Originally Posted by psu927 View Post
    I take it flashbacks weren't always used though correct? What are the hazards if I do not have them? I guess my main concern is if I am using too much acetylene and what size my current nozzle is as well.
    Nope. My current set of torches is a 50-60's era Harris that I got from CL. Local welding store had them rebuilt for 75 bucks, I added arrrestors, and they should last as long as I live!
    Arrestors stop the O2 and acetylene from mixing in places other than at the tip. You DO NOT want them to mix in the torch or the lines!! It basically stops the gases from burning back into the torch or hoses.

    Is your torch used? May want to rebuild it if any question of age or use.

    too much acetylene will lead to a dirty flame, too much O2 will put the flame out. There really is no such thing as too much O2 when hitting the lever, it will simply oxidize the steel and you will get a clean kerf and you will waste O2.

  7. #7

    Default Re: Cutting torch questions

    I guess if it sounds like a small jet engine before I hit the lever it's too much of both gasses?

  8. #8
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    Default

    The center hole os just for the oxygen (O2). The four smaller holes are the preheat flames. Adjust as you were doing, to get a neutral flame on the preheats.
    Find out what size tip you have, too big or too small will give you a hard time.
    Heat your steel with the preheet flames untill the steel is red hot and press the cutting lever to start the O2 flow. The hot steel will burn in contact with the O2. Progress slowly to make the cut. If you lose the cut, you went too fast. If the top edges of the cut are melted off you went too slow.
    Dan H.

  9. #9
    Gold Member Buckgnarly's Avatar
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    Default Re: Cutting torch questions

    Quote Originally Posted by psu927 View Post
    I guess if it sounds like a small jet engine before I hit the lever it's too much of both gasses?


    yes!, probably too much O2. And to be safe, NEVER EXCEED 15PSI for the acetylene. I have never used more than 5-7, should really never need more than that for cutting. It gets real unstable at pressures higher than that!

  10. #10

    Default Re: Cutting torch questions

    Quote Originally Posted by Buckgnarly View Post
    Nope. My current set of torches is a 50-60's era Harris that I got from CL. Local welding store had them rebuilt for 75 bucks, I added arrrestors, and they should last as long as I live!
    Arrestors stop the O2 and acetylene from mixing in places other than at the tip. You DO NOT want them to mix in the torch or the lines!! It basically stops the gases from burning back into the torch or hoses.

    Is your torch used? May want to rebuild it if any question of age or use.

    too much acetylene will lead to a dirty flame, too much O2 will put the flame out. There really is no such thing as too much O2 when hitting the lever, it will simply oxidize the steel and you will get a clean kerf and you will waste O2.
    Will it just leak if it needs rebuild?

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