[TheForge] Oxy/Propane reprise

Mon Nov 9 20:41:03 EST 2009

Hey guys,  I remember attending a demo of a propane cutting torch at a local welding supply party.  This thing, (I can't remember the name) but it worked on a venturi principle for the propane,  you just adjusted the O2 and the propane followed.  I tried it and it worked great on a 1" piece of steel.  Next, my wife was convinced to try it, (never cut anything except with a knife or scissors) and she did a perfect job.  I think the secret may be in the venturi type setup.

Ron Lass

> Date: Mon, 9 Nov 2009 15:35:59 -0600
> From: crosspein at sbcglobal.net
> To: theforge at mailman.qth.net
> Subject: Re: [TheForge] Oxy/Propane reprise
> 
> Since I already had the torch angle at a "push" angle of about 20 
> degrees, I'm going to assume that torch was too far away, and probably 
> in need of adjustment.
> 
> I had read on some mailing list somewhere (while trying to get as much 
> info on this as I could find) that the secondary flame envelope on 
> oxy/propane was hotter than the primary, so keeping the torch further 
> away (up to a point) was better than up close. I guess that's what I get 
> for trusting internet wisdom :-)
> 
> Too bad I have class tonight. I'd love to play with this when I get 
> home. But we're TIG'ing Al, and I find that great fun too, but I'll be 
> glad when the semester is over. I didn't get into the next session 
> (filled), and I'm not spending enough time with my hammer.
> 
> **Paul
> 
> Peter Fels & Phoebe Palmer wrote:
> > Paul:
> > That travel speed was much slower than it should be. Try tilting the tip 
> > in the direction of travel once the cut is started.
> > Adjust the torch when the oxy lever is depressed. There should be little 
> > or no feather. Crank the preheats up so you can proceed faster..go as 
> > fast as possible without losing the cut.  pf
> > 
> > Paul N wrote:
> >> Thanks Ben,
> >> There's no question that the wind was a factor, as the torch blew out a 
> >> few times with a gust of wind. I'm still a little unsure of how my flame 
> >> profile should look. I was setting the mixture so there was little of 
> >> what I would call an "acetylene feather" of I were using acetylene. But 
> >> those cones in the preheat flame were mighty small, maybe 1/8" to 3/16".
> >>
> >> I was successful in cutting my circle, I just had some difficulty a few 
> >> times. Actually, now that I gave it some thought, that I did cut about a 
> >> 90" long kerf, and while I don't know how fast I was moving, if it were 
> >> about 3 inches per minute, that's still about 30 minutes of continuous 
> >> cutting. And there were segments where I was actually moving along 
> >> pretty well for an inch or two before I got a little ahead of my heat 
> >> and had to pause.
> >>
> >> And I know I was going pretty slowly, particularly when I got "near the 
> >> end" and was worried that the change in balance was going to make the 
> >> thing move alot, so I was a little more outstretched, and consequently 
> >> less steady with the torch. (As it turned out, the work was sufficiently 
> >> secure, and as the cut completed, it didn't move much)
> >>
> >> It'll be a good week before I get a chance to try again. Gotta devote my 
> >> saturday this week to the UMBA fall meeting. At least I have a more 
> >> manageable piece to practice on now. A 4'x4'x3/8" piece is not that easy 
> >> to move around :-)
> >>
> >> Thanks again,
> >> **Paul
> >>
> >>
> >>
> >> Ben Barrett wrote:
> >>> Hmm.  My setup is almost identical to yours, and I have had good luck,
> >>> although there are some differences:
> >>> * I run my torch in a wind-free environment.  My own movements are
> >>> visible in the pilot flame of my fuel-saver, but not on the torch at
> >>> all.
> >>> * I have a smaller tip, #0/"aught" IIRC, but still a victor
> >>> oxy/propane tip on a clone torch body.
> >>> * I tend to keep my propane regulator around 3-5 PSI, and the oxy
> >>> around 20-30... sorry for the range here, but I honestly don't know
> >>> how accurate that is anyway (is an acetylene regulator but was new).
> >>> When the tip was new, I got about a 30" long flame, much longer than
> >>> anything I had seen on oxy/acetylene, very narrow and tubular and
> >>> well-formed, and I was told that I should be able to cut pretty far
> >>> away from the tip if I had good enough control to manage it.  The tip
> >>> has had some use now and not much cleaning but still maintains ~20" of
> >>> clean narrow cylinder of flame... now just recently I had taken to
> >>> running it slightly oxygen-rich, because of the increased intensity of
> >>> heat, which does seem to shorten the flame from its maximal length.
> >>> I might've been running the propane closer to 6 or 7psi in the
> >>> beginning, too, but have mostly been using this setup for heating (not
> >>> cutting) but the oxy lever is out of my way when the torch is clamped
> >>> next to the pilot.  I don't know what to suggest to you, since your
> >>> scenario sounds so similar, and hopefully I'm not overlooking any key
> >>> differences.  My initial level-setting procedure for the torch-body
> >>> needle valves seems identical to that of oxy/acetylene, I first bring
> >>> a fuel-only flame off the tip then add oxy.  Wind is a foe of either
> >>> =/
> >>> I have a feeling that propane mixtures need a little more "oomph" to
> >>> light, something about the fuel being so heavy and syrupy, but I can't
> >>> quite quantify that.
> >>>
> >>> Best of luck,
> >>>
> >>> Ben
> >>>
> >>> P.S. - my rig has cut before, and was reported by more experience
> >>> hands to be quite capable, and just fine as expected.
> >>>
> >>>
> >>> On Sun, Nov 8, 2009 at 7:16 PM, Paul N <crosspein at sbcglobal.net> wrote:
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