Problems with oxy fuel cutting.

[Wlhequipment]

Hi folks,

I’m having a problem cutting some 1/8” diamond plate steel. I don’t normally work with thinner materials, so I went to my chart, changed my tip and gas pressures, and went to cutting. Normally my cuts are pretty good, but with this stuff, the steel just re-welds itself right behind the torch as I’m moving along, and I have to go back and forth over the same area, and we all know hat that does. I spent an hour just cutting 2 circles in that diamond plate yesterday and it looked just terrible. I tried cranking up my O2 pressure, but that didn’t seem to do anything. 1/4”, 1/2”, 1” thick steel I’m fine. This thin stuff is baffling. What am I doing wrong?

 

[DDoug]

Cutting by hand or with a machine ?
Which way are you cutting the diamond plate ?
Post pix of cut edge please.

 

[Wlhequipment]

By hand, dragging and pushing. I’ll post a pic later, but it’s messy, slaggy etc.

 

[DDoug]

By hand, dragging and pushing. I’ll post a pic later, but it’s messy, slaggy etc.

I meant, dimples up or down ?
It sounds like your going too slow, and just melting.

 

[Wlhequipment]

I meant, dimples up or down ?
It sounds like your going too slow, and just melting.

Oh dimples down. I’m going back to the shop to catch up on some stuff this morning. I’ll try again and move a little faster.

 

[Peter from Holland]

What gas you use ? With acetylene you can get a sweet spot on the flame where it is long and loud ( mostly on a setting lower on gas and oxy)
Loud means more speed of the gasses It worked for me on thin material

Peter

 

[BT Fabrication]

what torch tip size? sounds like its too large. too big and it provides too much heat and melts the edges off and is able to cool behind it. Can also happen from moving too slow, but most likely wrong size tip orafice. try a smaller one.

 

[Pete Deal]

I don’t cut much anymore with oxy-acetylene since I got my plasma cutter but I’ve had this problem before myself with thinner materials. Cutting by hand. Somewhere along the line someone told me to angle the torch over some so it points into the cut at maybe 30-40 degrees. This helps.

 

[Wlhequipment]

I can’t figure out how to post images, it always says “image too large”. Anyway, I’m set up like the book says for 1/8”. 000 tip, 25psi Ox, 5psi acet. I get the same result whether I go slow or fast, clean off the mill scale or not, start on either side of the sheet. Also, same setup, I can cut 16ga and 3/8. A little slow on the 3/8 but it’s fine. This is bizarre. Never seen this before. I used this diamond plate on a project a year or so ago, and it welds beautifully. For that project, I didn’t use the torch to cut it, I used grinders and saws and whatnot. What the heck is going on?

 

[pat pounden]

Oh dimples down. I’m going back to the shop to catch up on some stuff this morning. I’ll try again and move a little faster.

just use an import plasma for thin stuff!!

 

[idacal]

its the thin material, I dont think you can travel fast and smooth enough with a hand torch to get a good cut with oxy.

 

[Wlhequipment]

I tried the angle thing. Good idea but no change. I can cut thinner and thicker stuff no problem, using the exact same setup. Screw it. I just needed to cut one piece for one thing. I’ll just use a die grinder. I give up. Thanks anyway.

 

[M. Moore]

WLhe,
I had the same problem when trying to cut any 1/8” thick steel material with my oxy acet and now my oxy propane torch. I have a small cnc torch table so I could vary a lot of the parameters. I tried everything to get a decent cut but could not achieve anything close to what I get with thicker materials, 1/4,1/2 and 3/4” primarily.
I would get lots of slag buildup under and the cut would weld itself back together.

If I tried faster then I would lose the cut. I never tried to cut thinner than 1/8”. Turn down the heat, lose the cut, up the oxy pressure, no change. I could also easily change speed and height of torch with no change in cut quality, very frustrating. I even tried using water to keep the steel cool near the cut, very tricky to do and not great either.
I can get near perfect cut quality in 3/4” plate on my torch table, so good I can grind and sand to a perfect flat edge surface very quickly and I have to do that often for my furniture work.

I could actually get shapes cut out of the 1/8” (10 or 11 gauge) but the cleanup was terrible and now I use my plasma cutter with an adapter to fit to my torch table. It works very well (cut quality) but is a bit clunky given I don’t have the proper machine torch yet, just the handheld.

Does anyone else find it strange that you can get 1/8” flat bar or 1/8 wall sq tubing but you can‘t buy a sheet of
1/8” thick steel plate? Just plain weird?

 

[john.k]

If you call it 3mm ,then there is downgrade steel sheet that thickness all over Fbok marketplace............commonly use for truck and trailer decks.........its also quite possible steel is no longer formulated for oxy cutting as everyone uses plasma for that thickness.

 

[memphisjed]

Does anyone else find it strange that you can get 1/8” flat bar or 1/8 wall sq tubing but you can‘t buy a sheet of
1/8” thick steel plate? Just plain weird?

11 gauge steel. Square tube is 11 gauge, round is 10 gauge. Why, idk.
Flat bar comes from different mill where the tape measures are in proper units.

 

[john.k]

If thin steel rewelds behind the cut,the preheat flame is too large.........I think there used to be single hole preheats for sheetmetal......... everyone uses plasma now ,so likely there is no demand for the tips.

 

[DDoug]

You need to increase the preheat flame.
Moving fast enough to keep the reaction going, requires
MORE preheat not less.
"Hot & Fast".
I ran 1/8" on my small CNC, but you need to pay attention to it.

One trick I recently learned for problem (nasty slag, etc.) Oxy cutting, is to light the torch, set the preheat flame, and run it around the part to clean the cut line before going back and cutting it with the blow oxy on.

 

[Peter from Holland]

You need to increase the preheat flame.
Moving fast enough to keep the reaction going, requires
MORE preheat not less.
"Hot & Fast".
I ran 1/8" on my small CNC, but you need to pay attention to it.

One trick I recently learned for problem (nasty slag, etc.) Oxy cutting, is to light the torch, set the preheat flame, and run it around the part to clean the cut line before going back and cutting it with the blow oxy on.

I used to do that with the blow oxy on
Takes off all the slag On thicker material though
Peter

 

[cyanidekid]

is it rusty? rust will do that.

I have to agree with john.k here, I've actually blocked off some of the preheat orifices and gotten good results.
I absolutely agree about running the preheat only along the cut line first though, DD. I think what's going on there is there's water trapped in or under the mill scale, and you can actually see and hear it popping as it vaporizes. if it does that while cutting it disrupts the cut, especially on the thinner stuff.

try the smallest tip, the tables tend to be "over rated",
and/or REDUCE preheat and see if it helps (the smallest flame that is safe and stable while cutting).
angle the torch pointing the flame forward in the direction of the cut by 40 deg or so. this is like cutting thicker metal in effect.
CLEAN the metal, take off all paint, rust, scale along the cut line.

sheet goods as memphisjed said, comes in "gauge" thicknesses and 11 Ga. is a nominal .120

 

[M. Moore]

I tried everything when I was attempting to cut 10 or 11 gauge sheet. Hot and fast doesn’t mean anything unless you have some evidence to back it up? What size tip and how fast was the travel speed?

11 is 0.132 and 10 is 0.118 and that is quite accurate when I measure my sheets.

I was cutting brand new clean sheets and there is no way I would be removing mill scale before cutting any new sheet.
The torch on a CNC needs to be exactly vertical, not practical to angle it 40° unless you are only making straight cuts. The OP was hand cutting so could apply to his situation. However keeping a torch angled correctly around a circular shape is quite difficult. Those that suggest the method should try it first on a round shape.