Pictures of a 3/4" plate cut with Oxy/Acet. vs Plasma Cutter

Without a doubt, yes. My problem is that my hand is unsteady.

i

What size tip, acet pressure and O2 pressure? As a guess, I would have started with a #3 tip, 4psi acet, and 50# O2. You can do much better than that with OA.

Steve

Sort of what I thought too. It's cut, but a bit of hack job on the OA side. I've never run a plasma, but I know I can get a pretty clean cut with OA when set properly.

I just had to cut an 1" shaft in the field and the end cut looked almost the same as if I had done it on my cold saw (aside from the rolled edges instead of a crisp cut edge like a true blade cut.

FWIW: It's not all that hard to cut a nut from a bolt and still be able to use the bolt afterwards with very little damage to the threads. (For those who haven't tried it)

It's a skill like any other that when one masters can be quite impressive. (and I am far from mastery)

JW

Is this your first time cutting? The first time I used oxy-acetylene it was definitely messier than that.

Best wishes,

Chris

First time with acetylene, yes (aside from a very quickly aborted attempt at school).

Steve, I tried this at my friend's and I think that his nozzle is smaller than #3.

My nozzle is #3 and I will try the exact settings that you suggest, it will be a few days though. I saved your post for when I will try.

Not bad then, I would say. But perhaps you had a better instructor than me. I don't think the guy who showed me knew much more than I did. Just that you used it to cut stuff :-).

Chris

Well, I had my ploasma cutter for a while and I did some plasma cutting before, though never of such thick material. My plasma cutter can cut at 100 amps at 100% duty cycle.

I got out of my way to avoid machines offering less than 100% duty cycle.

Chris

Looks great, I will try to practice some more...

Hints: always use 4 psi acet, and turn up the O2, as that is what blows the molten metal away. On tips, use 1 for each 1/4". Hence, 3/4" plate would use a #3. Angle the torch backwards a little from the vertical with the tip being pointed forward. Watch the sparks and don't travel too fast. When done, look at the vertical striations on the cut piece. If they are straight, you got the O2 right. If they are curved, you have the O2 set too low, or are traveling too fast. It's hard to use too much O2 with thick stuff, but with thin stuff, it makes a lot of difference. You want straight lines. And no big globs of spongy stuff or a lot hanging from the underside. Something like this:

Keep practicing. It's tricky and frustrating.

Steve

Kick up that O2 to at least 40. The one I did today, and posted pics of, I used 50#.

Steve

On Tue, 11 Nov 2008 23:05:24 -0600, RoyJ wrote (in message ):

when using a straightedge, put something under it, like 1/8" washers or spacers of some kind, to keep the straightedge up off of the metal that is being cut. Also, the straightedge needs to be heavy enough that it will stay put, so it does not move around as your torch is guiding against it. tom koehler

I usually use a piece of angle clamped to the piece being cut.

On Wed, 12 Nov 2008 20:56:02 -0600, Ignoramus7090 wrote (in message ):

yeah, that is good, but you want to have some kind of spacers under the angle iron, so there is a gap of at least 1/8" between the straightedge (angle iron) and the surface of the metal being cut. Assuming you are using either oxy-acetylene, or other oxy-fuel torch, you will notice that the preheat jets around the center cutting jet will make a nice symmetrical star flame, splayed out around the cut line. If the angle iron guide is in contact with the surface being cut, your preheat jets will not adequately heat the metal for cutting, and the quality of the cut will be impaired. I used 1/8" or

3/16" wire, bent in a "V" shape, to raise the straightedge up off the metal surface. Any place where you have put a clamp to hold your angle iron down... put one of these V spacers between the metal and the straightedge in such a way that the spacer is not exposed or interfering with the travel of the torch. Your cut line will be uniformly preheated all the way around your cutting jet, and the cut will be cleaner and neater. tom k.

This was a very good explanation, obviously does not apply to plasma but very applicable to O/A.

If you plan to do much OA cutting, there are torch guide kits available. The most common is a circle cutter, but the same kits will generally be able to set up for straight cuts. I have used the circle cutters and gotten very nice results.

Similar stuff is available for plasma cutters as well. I mostly use a piece of angle aluminum for straight plasma cuts.

Good Luck, BobH