acetylene torch settings

MtMan

Member
I have been cutting with a acetylene torch for a long time, but lately I have not been able to cut like I would like. What ate the settings for Acetylene and Oxygen supposed to be. I understand there will be different ideas, but I would like to get close to the settings as possible. Thanks in advance.
 
With a Harris set, and a 5 hole preheat tip I run 8 acetylene and 35 Oxy if cutting up to 3/8. For 3/4 inch plate, I use 45 psi oxy. Jim
 
Thanks for the comeback, and that's close to what I use. Maybe it's my old age getting in the act.
 
We were always told to never go over 10 on the acetylene,the oxy. varies depending on the material thickness,but somewhere around 30-35 usually is about right.
 
Every time someone asks this question, I?m reminded of when I worked on a 50 man rail road crew for one summer between college. We had 2 foremen on the project. One was a ?know it all? everybody hated and the other was a good foreman that everybody liked. The crew member that normally torch cut the rail at the end of the day, was absent for some reason. Mr know it all (Mr KIA) foreman asked if anybody knew how to use a torch? I know there was at least 10 farm boys, me included, that knew how to use a torch. But nobody would volunteer for Mr KIA. So MR KIA asked how to set the pressure? Again nobody volunteered. So he turned the Acy to the red line 15 psi. But the O2 didn?t have a red line so said if 15 is good for the Acy it must be good for the O2. When he lit the torch and a 10 foot yellow flame came blasting out of the tip. He knelt down and attempted to cut the rail. I wasn?t sure if I should look for a fire extinguisher or find a place to take cover. About that time the good foreman showed up and looked right at me and said "Why aren?t you cutting the rail"? I said If YOU ask me, I will. He knew nobody liked Mr KIA.
 
The other posters have the setting pretty well covered. I would add checking your cutting tip. They need cleaned and reshaped to really cut well. I do not know what torch your using but new tips are not that expensive.
 
Just in case you do not know, acetylene is unstable over 15 psi,that means it can explode. I run 10 psi and around 8 psi on the acetylene. Watch some youtube it will help.
 
Well, it depends on the manufacturer and tip. The manufacturer of your torch should have a published table. I was able to find the tables for Smith, Harris and Victor:

Smith (Miller):
<a href="https://equiptoweld.millerwelds.com/pdf/spec_sheets/Cutting_Welding_Brazing_HeatingTip_FlowPressure_Data.pdf">https://equiptoweld.millerwelds.com/pdf/spec_sheets/Cutting_Welding_Brazing_HeatingTip_FlowPressure_Data.pdf</a>

Harris:
<a href="https://www.harrisproductsgroup.com/~/media/Files/PDF/Requested%20Resources/TIPSonCUTTING.pdf?la=en">https://www.harrisproductsgroup.com/~/media/Files/PDF/Requested%20Resources/TIPSonCUTTING.pdf?la=en</a>

Victor:
<a href="http://www.keengas.com/technical-tips-files/index_29_760312311.PDF">http://www.keengas.com/technical-tips-files/index_29_760312311.PDF</a>

Something to remember is that once you start cutting, it's all about the oxygen. You can even shut off the acetylene and the torch will continue to cut on oxygen alone, if it's getting enough oxygen. And of course the adjustment range for acetylene is small, typically 5 to 10 psi.
 
I've found not only the tip can cause problems, but the orings behind the tip, and where the cutting head attaches to the handle are critical. Any leakage will cause the torch to not burn properly.

Also the valves in the cutting head, the oxygen valve, and the one actuated by the handle, need to work perfectly.

The orings and the valve tend to degrade slowly with age.
 
Mine has been sitting on 10 and 40 for years and I cut from 1/8 up through 1 1/2 in plate. Just change the size of tip, also heat with a 150 rosebud. Smooth cuts are made by a clean tip, steady hand and the correct travel speed. Practice, practice and more practice.
 
Acet. has a limit but the oxygen does not .Turn it up as high as you need to cut the thickness of plate. Use 100 psi if you have to. 6 and 25 to start with { that will cut most plate] The tip for cutting 4 inch plate would be huge as well.
 
Somewhere I have read that Acetylene is actually mixed into alcohol when compressed in the cylinders. I don't know what kind of alcohol.

If you draw the acetylene out of the cylinder too fast, the alcohol comes out too and that is when you start to have problems. I am thinking you aren't supposed to draw more than 5 psi from a normal acetylene cylinder at any given time.
 
> I am thinking you aren't supposed to draw more than 5 psi from a normal acetylene cylinder at any given time.

You're confusing acetylene pressure with drawdown rate.

Acetylene is unstable at pressures over about 15 psi, which is why it's important to keep the acetylene regulator set below 15 psi. But the pressure in the cylinder is much higher. This is accomplished by dissolving acetylene in acetone. When your torch is in use, the acetylene bubbles out of the acetone much like carbonation bubbles out of a soda. But if acetylene is drawn too rapidly, acetone will be drawn out of the cylinder, through the regulator and out the torch. To avoid this, it's important to never draw acetylene at a rate greater than 1/7th of the tank capacity per hour.

You're unlikely to exceed the maximum drawdown rate while cutting, but it can happen when heating, particularly with a rosebud tip. The drawdown rate is pretty much independent of the regulator pressure and mostly depends on the tip size. You can reference the tables I posted in my earlier post to determine the acetylene consumption rate of your particular tip.
 

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