Cutting Tips Oxy/Acetylene

Ok... you guys have been great. Tips received here have helped me become a better welder, helped me make my HF flux core into a better rig, and guided
me towards selecting my Miller w/ spool gun for aluminum.
Now here is the deal. I never really learned to cut well with on O/A torch. I can patch thin sheet metal with one, but cutting seems to elude me. Sure I can whack through a piece of steel and make it into a smaller piece of steel, but my dad can cut out the top out of a barrel and make it look almost clean without using a grinder on it afterwards, and I have seen guys cut C-channel and I-beam and it looked good. Most of the slag could be knocked off with a hammer. Hardly any grinding needed at all. When I try a cut like that it looks like a lava monster chewed on the end of the piece and spit it out after a while.
Then I read stories about cutting steel a foot thick with O/A and just I am amazed. I just want to do a decent job of cutting garden and farm variety steel. Most things I use a chop saw, or a cut off wheel in a cheap circular saw for so I get good cuts, but sometimes those things just won't fit where you need them too. Even a Sawzall with a "Torch" blade won't fit everywhere. Sometimes an O/A torch is the still the best tool for the job.
Yes I have a cutting head, and I think I have the right pressure settings, but you guys tell me (if you will) and then I'll know.
Thanks Bob La Londe www.YumaBassMan.com
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Go to Lincoln, or maybe your local shop has the guide.
Simply put, use 4# acetylene on EVERYTHING. Never change the gauge. The O2 is what does the cutting, and that pressure increases as the thickness of metal increases.
Some of the tricks: Wait for the metal to become hot before hitting the O2. Look for color. Buy a tip cleaner and tip nipper and keep them clean. Use guides like angle iron for long straight cuts. Use any cutting aids you can find including resting your hands on the metal to keep the shake out. As with welding, watch what the O2 is doing. It's like the puddle. If it's blowing cleanly through, you're going to end up with a good kerf. (google that and understand that) Don't obsess about slag. Ideally you won't get much. You shouldn't have much on top, and if the stuff on bottom can be knocked off easily, your settings are right. You should end up with a clean cut, smooth kerf, and no surface or underside slag. If you do, something is wrong. That something could be wrong pressure, wrong tip size, wrong torch angle, wrong torch speed. If you get it on top, you aren't using enough pressure to punch through or moving too fast. If you have ever seen the smooth kerf of a piece cut with a track torch, that's what you're aiming at, but hand cutting is hard to do that. After that, you want straight lines through your material and not arced lines. If the lines are arced, you are using too little O2 or going too fast. Examine each cut afterward, assessing how much slag there is, how easy or hard it is to get off, and the lines of the cut (kerf) Then adjust. Learn to do it right and try to do it right every time instead of just good enough. Clean surface rust, as that, particularly the sheet stuff, is very hard to cut through. Grind a line into it if you have to. Use good markings, either scribing heavily or a hefty soapstone line.
HTH Steve
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Bob La Londe wrote:

I worked as a shipfitter for 13 years back in the day. My cutting torch was my #1 tool. I got to where I was reasonably good with it. But later when I'd done a lot of welding (had trained my eye/hand muscles to move better) I was much better at cutting with a torch freehand.
The first suggestion I have is to try to borrow or get some time cutting with a top quality pair of regulators. Cheap regulators will screw anyone up. If your regulators are good ones (post the make/model data here if you don't know) then they still might not be in good repair. All your gear has to be right.
The second suggestion is to get a tip chart for your kit.
The third suggestion is to not try steel that's too thin or too thick at first, because those cuts take more skill. Cutting steel in the 3/16 - 3/8" range is easiest. A great thing to do is to get an old pieces of scrap structural steel, something like 6x6x3/8" angle iron maybe six or eight feet long, and just do torch cuts cutting off about 1/4" each time, one after the other after the other. In other words, practice. If you do have to cut thin steel, angle the torch - it makes the effective thickness larger.
Use the correct tip for the size steel you're cutting, and use the correct regulator settings. Make sure your settings are when the gas is flowing, not with the torch valves closed.
I'm going to guess you're using a Victor torch setup or clone. Here is a tip chart to get you going: (this will read best with fixed-width font)
Victor Acetylene Cutting Tip Chart - Cutting Tip Series 1-101, 3-101, 5-101
METAL TIP OXYGEN FUEL SPEED KERF THICK. SIZE PSIG PSIG I.P.M. WIDTH 1/8 000 20-25 3-5 28-30 .04" 1/4 00 20-25 3-5 27-30 .05" 3/8 0 25-30 3-5 24-28 .06" 1/2 0 30-35 3-5 20-24 .06" 3/4 1 30-35 3-5 17-21 .07" 1 2 35-40 3-6 15-19 .09" 2 3 40-45 4-8 12-15 .11" 3 4 40-50 5-10 9-12 .12" 4 5 45-55 5-10 8-11 .15"
I see a lot of backyard guys who have a #2 tip on their torch, with the gas settings way off from what they used to be, and they basically meatball their way through anything and grind their a** off to make the parts usable. That's fine if you don't care about your craft.
There are some good books out there on oxyacetylene torch cutting. Try your library, or your library's interlibrary loan feature.
Stay at it. This is a skill that takes awhile to develop.
GWE
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wrote:

As a side note..most of the oil field welders around here, will keep a 00 or 0 tip in the torch for 99.99% of their cuts with about 25psi on the O2 and 5 psi on the Ace.
So do I. shrug..for what its worth.
Gunner
'In the first place, we should insist that if the immigrant who comes here in good faith becomes an American and assimilates himself to us, he shall be treated on an exact equality with everyone else, for it is an outrage to discriminate against any such man because of creed, or birthplace, or origin. But this is predicated upon the person's becoming in every facet an American, and nothing but an American... There can be no divided allegiance here. Any man who says he is an American, but something else also, isn't an American at all. We have room for but one flag, the American flag... We have room for but one language here, and that is the English language.. and we have room for but one sole loyalty and that is a loyalty to the American people.' Theodore Ro osevelt 1907
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Well first off you might make sure you don't have a divergent bore high speed machine cutting nozzle as those won't work unless the pressure is really up there.
second preheat a few inches and cut a few inches try that
The suggestion of cutting pieces of the end of a bar or something will essentially pre heat for you.
A lot of it is holding the thing steady. putting a block under your hands may make it easier.
And the suggestion of grinding down the line is a good one.
Too much heat isn't good either.
How many pre heat holes do you have in the tip? if it is les than six I think you are supposed to adjust it so one of the flames is along the line of a square cut but the other way for a bevel cut.
I am sure there is more, I don't really pay attention the the numbering systems more the number drill size of the center hole. #60 is pretty common and likely the 99% size (well the gas shop seems to think the #53 is the most common and they stock a bunch of little wire feed welders which sure aren't rated for that size steel) it is rated for perhaps 3/8 to 5/8 it is near 0 size for a lot but 4 for pruox oxweld.
I will believe the line about the barrel top if I see it. he must be cutting against some portion of the barrel acting as a chill bar or something.
Fran
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My usual list of tips:
You must be absolutely steady and uniform!! Use a piece of barstock as a guide, practice pulling the torch towards you while maintaining the height with one hand and hitting the lever with another hand. This is the ONLY time I recommend having alcohol while working but half a beer may relax you enough to make a difference!!
Tip has to be clean. REALLY clean.
practice on a piece of 3/8" plate.
4# on the acet, try 20# on the O2. Open the O2 valve on the torch body wide open, crack the acet valve a bit, light torch, add a bit of O2 from the cutting head valve, open the acet full. Adjust the cutting head O2 to make the inner and outer blue flames the same length. This is neutral flame and the hottest flame. Should be something like 1/4" to 5/16" from tip.
Set the tip of the inner flame on your workpiece (ie the 5/16" from above), find an edge to get started (You can plunge cut but not as a newbie!) Once you see a tiny puddle form, hit the O2 lever and start pulling SLOW and STEADY. The object is to get a cut that stays lit for the full length. If keeping it lit is a problem, up the O2 pressure to 25 or 30 psi.
Once you get a cut to stay lit for several inches, try to speed it up.
Once you get a full cut, it's time to fix the problems: your back edge probably looks like c**p. Check to see that the cut is in a straight line: if not, your guide needs work. If you have trouble losing the cut, you need to work on slow and steady. Take a look at the lines in the cut: they should be straight with just a hint of a bend at the far side. If no bend, reduce the O2 pressure. If gobs of slag, reduce the O2 pressure.
The object is to just use up the O2 as it reaches the far side. A perfect cut is much smoother than a hacksaw cut. A perfect cut has a very slight rounding on the near side from the preheat flame, a faint burr on the back side.
Bob La Londe wrote:

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Get a size 0 tip, acet 4#, ox 30#. Main thing is the flame adjustment. Here's a quick way I do it. Of course, set your regulators to 4 and 30 and let some gas off to fill the lines. Close all three valves. Open the 02 on the hose, but not the one on the torch. Open the acet and strike. Come up or down on the acet knob on the hose until the flame doesn't make floaty black boogers. Open the 02 on the torch until you get blue cones from the holes around the center. Squeeze the handle and watch the blue cones. Look at the cones. Let off handle and adjust 02 until they don't change from when you aren't squeezing the handle and when you are. Go from there.
Cutting thin stuff requires attacking from an angle less than 90. You'll be pushing your way into your piece, and you will see the 02 jet cutting the metal a pretty good distance in front of it. Angle will be like ten or fifteen degrees. You can even let the tip touch the piece. That's the way I cut .120" tubing so it looks darn near a saw cut.
Go get some scrap and practice. Be safe. Check all connections with Windex, and watch so the slag doesn't fall on the hose in a moment of inattention. Have a hose at the ready and pressurized. Wear eye protection, and I wear ear plugs, the horseshoe clamp kind because dingleberries (flying molten bb's) are always attracted to ear canals for some reason.
Be sure to shut your bottles down when you're finished and back off on the t handles. duh!, but I can't say how many times I've seen them run out overnight, and I won't admit how many times I have done it myself.
Keep us posted.
Steve
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Another one of those things that can be explained with five e mails from six people, and shown to you in the time it takes to drink two beers. Try to find a welder in your town, and get it the easy way.
Steve
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Sounds like I have been using too much O2 for most things. Will experiment and get back with you.
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20-30# will cut most anything up to one inch. Vary with the size of the tip, and remember to keep those tips clean, poking those little wires in there often. And don't forget about the big center hole.
Steve
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I agree with most of the previous replies but would like to add a few humble opinions,
Beginners view cutting as melting and blowing rather than the more correct concept of burning.
Too much O2 pressure should not cause a poor cut (if the tip is clean) but will be a waste of increasingly expensive O2.
Most people use tips which are larger than necessary which wastes both acet & O2, and often results in damage from too much preheat. I prefer to use machine tips which have (usually 6) very small preheater flames. These require a very steady hand but make a nice clean cut, especially in thin material or pipe. Slightly higher O2 pressure is required if using very small tips or long hoses.
Proper cleaning of the cutting orifice is the most essential factor in making a nice clean cut. The tip cleaner must be moved STRAIGHT in and out without belling the orifice. Over cleaned tips often have belled or damaged orifices which cause turbulence and deflection of the cutting O2 stream. Older tips can often be salvaged by shortening the tip with a smooth file in order to remove the damaged or belled part of the orifice, the edge of the orifices should be very square and sharp.
The cutting stream should be checked by observing the cutting stream after lighting the torch, it should be seen as a dark smooth stream in the core of the preheater flames, you may need to hold the flame against the right background to make the stream as visible as possible. The difference between a dirty and a clean tip is easily seen with this test.
Always make a dry run to check body position and freedom of body and hose movement. For added hose flexibility, I like to use a smaller ~10' whip hose between my torch and the larger ~100' main hose to the regulators.
Cut ON the center of the line and not beside it. Allow for the curf width in layout if required but normally this is not needed.
Good luck, YMMV
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says...

I know a lot of weldors who "split the dots" when OxyFuel cutting. For precision cuts, the shipfitters layout with a soapstone line, then center punch along it, spacing their punches approx. 3/4 inch apart.
Those punchmarks are what get cut in half.
I know just enough to be dangerous with oxyfuel cutting, and know nothing about welding with it. Practice, practice, practice. That's how you get good at anything.
--
Tin Lizzie
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On Sun, 09 Aug 2009 08:20:38 -0700, Bob La Londe wrote:

I can _not_ cut a straight line with a cutting torch -- my hands shake too much. Perhaps I could if I were willing to drink a few beers and then go out to the shop -- somehow that doesn't appeal to me, though.
But I can do an acceptable job if I use a guide.
--
www.wescottdesign.com

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After you have depressed the handle, adjust the oxygen pressure until it forms a nice jet which does not break up. Too much pressure is just as bad as too little. To cut thin sheet, you can angle the torch in the direction of the cut so it effectively sees a thicker sheet. This gives a cleaner cut, but you have to travel fast.
--
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