Oxy-cutting advice please

What am I doing wrong please!!
I need to cut some relatively thin sheet (2mm) mild steel using an
oxy-acetylene straight line cutting machine (BOC PUG). I know really the
sheet is a bit thin for this. I'm using the smallest cutting nozzle I can
find (1/32"), with 5 psi Acetylene and 20 psi Oxygen.
As the cut proceeds it fills back in and re-welds behind the cut. I've tried
speeding up to the point that the pre-heat isn't enough and the cut stops,
and slowed down to the point that the kerf is too wide. I've raised the
nozzle, and lowered the nozzle. I've raised the oxygen pressure to 30 psi
and lowered it to 10 psi bit still I get a nice straight line of weak
re-weld.
I don't want to have to go back to the jig saw - HELP !!!!
Andrew Mawson
Bromley,
Kent,
UK
Reply to
Andrew Mawson
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Don't have one of these but have seen one used. Try to put some bar stock or something under one side of the cut line so as the cut proceeds gravity will help keep the two pieces apart. Maybe a little weight on the piece that is off the table? Doug
Reply to
Douglas R. Probst
Try rotating the nozzle, not just lifting it up. It's almost like you are trying to create a groove in the steel rather than cut it. You always have to have the nozzle pointed in the direction of the cut so it does not work very well for sharp curves or really restricted access situations.
Mike
Reply to
Mike
Try a sheet metal cutting nozzle. Rotty
Reply to
Rotty
If you don't have a sheet metal cutting nozzle handy could you apply a slight pressure (up or down) to one side to hold it apart when it is cut? I don't know how this would work. Might have to weight the other side in order for it to spread, as with snips. . . . But then, if it is corrugated . . .
Rotty wrote:
Reply to
Al Patrick
The torch pressures sound right. You should select a double zero or even triple zero tip. The torch head should be pointing ahead as much as possible. If the torch could be tilted thirty degrees to the surface of the sheet that would be ideal. You want to throw the preheat forward. Don't use excessive preheat. You want enough preheat to burn the steel but not melt it. Too high a preheat will cause that re-welding effect. Go as fast as you can without losing your cut. In many cases you can do a better job with a steel bar guide , a small tip and a hand held torch pulled towards you as fast a possible. The tip of the torch should almost touch the plate with its side when tilted. Randy
Reply to
Randy Zimmerman
Get a sheet cutting nozzle. Fits your standard torch, has a cut jet that points sideways. They're not much good on tight curves, but they're fine for straight.
Reply to
Andy Dingley
Couldn't you just use some of those air powered snips and zip right down a straight edge?
rvb
Reply to
Rick Barter
When I have to cut steel less than 3mm thick, I found the most success by hand, using a guide bar. As Randy pointed out, you need to incline the torch in the direction of cut, flame pointing forward, 60 to 80 degrees from vertical. As well, you need to move as quick as possible, without losing the cut.
Reply to
Wayne Bengtsson

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