oxy/act torch ?

[morpheus]

I've been using an oxy/act torch for several years now and can cut up to say 1/2" plate quite quickly and easily with a good clean cut.

But I just last night finished up cutting a piece of 1" plate that just about drove me crazy. After trying with my normal settings I turned the oxygen up to about 45 psi which really helped alot. but my main problem was that occasionally when I'd "loose" the cut. Perhaps there is technical term for when you go to quick and outrun the cutting ability of the moment ?

Anways, on this thick plate it was incredibly difficult to "restart" my cut because my cutting line would get all filled up with slag. I realize that this slag was the reason for my difficulty but why is slag such a problem ? and what can I do to not have such difficulty in the future ? (besides the obvious of not going to fast in the first place) though I don't plan on cutting any 1" plate any time soon.

thanks.

- jack

[Sberry]

On thicker plates (above half inch) it really helps to burn the mill scale off first and to preheat the plate. Warm it good from both top and bottom if you can. You should up the tip one size for that thickness and take those old tips you have had for years and pitch them. Do yourself a favor and buy a couple of new ones. Its difficult to solve cutting problems with an old eroded tip.

[morpheus]

thanks for the help. now that you mention it i think the lack of good preheat on the thick plate is what my real problem was. I could get the cut started but It wouldn't penetrate much. thus creating a big slag mess.

I was using a #3 tip, so, it was plenty big.

- jack

[Aeroweld]

Cutting !" is a good test of of your cutting skills. SBerry has some good suggestions in making sure your tip is in top notch condition. and the mill scale, if present, is burned off. Personally, I don't use any "preheat" unless the plate is very cold and I want to remove the moisture or if I happen to have a tip that is a bit undersize. But that's me.

Torch tip sizes seem to vary from manufacture to manufacture. Just because it a #3 Victor might not translate into a #3 Harris or National. You want a pretty big lance hole in the tip for 1" plate.

With the proper tip you can cut down on your O2 pressure and get a better cut. Yes, I said DECREASE the pressure. The biggest misconception out there, to the point of being an "Urban Legend", is that if you are getting weld back in the kerf is to increase O2 pressure.

WRONG, WRONG, WRONG!

You actually want to decrease the pressure. With the proper tip, 35-40 psi is plenty pressure to cut 1". Too high of pressure actually blows the metal back into the kerf thereby closing it up. You will know that the pressure is correct when the kerf doesn't close and when you are burning, the sparks coming out of the kerf are close to a 90 degree angle to your direction of travel; ie almost blowing along the bottom of the plate.