O/A Cutting of 3/32" steel & slag...

[Brad Heuver]

I have been having trouble getting a 'drop free' cutout on some ~3/32" thick
scrap steel. The cut always seems to re-weld itself together (the slag I
presume) after the cut has progressed about 1/4" further down the line.
I am using a Harris torch, equipped with a 000 tip (I also tried a 00) I have
tired Act pressures from 3-8 psi, and various levels or preheat flame. Ox
pressured from ~ 6-25 psi. I'm getting what seems to be best results so far
with a small preheat flame and about 5 psi Act, and 12-15 psi O2.
The shapes are various small outlines, all smaller than a softball or so. I can
usually pound them out of the parent metal with a chisel and hammer, but can't
get near a clean drop.
Any suggestions? I have varied the torch speed all over the map, from real slow
(much worse re welding) to quite fast (then I lose preheat and the cut)

[Grant Erwin]

This is awfully thin metal for torch cutting. It sounds like a 000 tip
is
too big. Have you considered a big air nibbler? 3/32" is practically
sheet
metal .. you might also get decent results with a good power jigsaw with
a 24T blade.

I think it can be done with a torch, but you just have to have really
excellent skills. I think I'd try doing the initial preheat, pull the
oxygen trigger to start the cut, and immediately lift the tip while
moving the oxygen stream rapidly down the cut line. If you do the bulk
of the cutting at least 1" from the tip, it might cut cleaner. Of
course, you have to have CNC hands to make an accurate cut this way.
I used to work in the big shipyards in Seattle, and they had guys who
only cut steel with torches, all their lives. The cuts a good burner
can make are incredible.

The only other thing I can think of is that your regulators might not
be working as well as you think they are. I used a cheap set of
regulators at home for a couple of years and couldn't get clean torch
cutting no matter what I did, then I got a good set of regulators and
the problem largely went away ..

Grant Erwin

[Seppo Vataja]

Angle the tip forward about (45 deg)
Push the slag ahead of the cut
this also has the effect of making the steel seem thicker to the torch
you also have to move faster

[Frank Sennett]

You'll have better luck cutting thin stuff if you tip the torch into the cut
at maybe 45-60 degrees and feed along as rapidly as possible without losing
the preheat. That keeps from having trailing heat from the flame that
rewelds the material.
****The General****

[Brad Heuver]

In article <7l0fcc$em1$1...@bgtnsc02.worldnet.att.net>, "Frank says...

**** Thanks for the tips so far, I will try angling the torch this weekend!

[GAD0GA]

>Any suggestions?

Yes, I can cut 1/2 inch steel with 2 psi. Lower your pressure, and tilt the
torch into the uncut steel, and go like hell.
Be sure you adjust your torch to a neutral flame. This is attained when the
preheat jets do not change size when the O2 trigger is pulled.
http://members.tripod.com/~arkansascody/

[1viki...@home.com]

Just a thought do you have the primairy ox valve open all the way?
if not try it and see what a difference it makes.
George
On 25 Jun 1999 08:05:39 -0700, Brad Heuver <Brad_...@newsguy.com>

[Mike Graham]

On 25 Jun 1999 08:05:39 -0700, Brad Heuver wrote:
>I have been having trouble getting a 'drop free' cutout on some ~3/32" thick
>scrap steel. The cut always seems to re-weld itself together (the slag I

>presume) after the cut has progressed about 1/4" further down the line.
>I am using a Harris torch, equipped with a 000 tip (I also tried a 00) I have
>tired Act pressures from 3-8 psi, and various levels or preheat flame. Ox
>pressured from ~ 6-25 psi. I'm getting what seems to be best results so far
>with a small preheat flame and about 5 psi Act, and 12-15 psi O2.
>The shapes are various small outlines, all smaller than a softball or so. I can
>usually pound them out of the parent metal with a chisel and hammer, but can't
>get near a clean drop.
>Any suggestions? I have varied the torch speed all over the map, from real slow
>(much worse re welding) to quite fast (then I lose preheat and the cut)

Tilt the torch. Big-time. Almost flat. You'll want the edge of the
torch tip to touch the metal. This way, you're not cutting 3/32", you're
cutting about 3/16", and it's way easier.

--
Mike Graham, mikegraham at sprint dot ca
Caledon, Ontario, Canada (just NW of Toronto).

Raiser of animals. Weldor of metals. Driver of off-road vehicles.
Writer of FAQs. Keeper of the faith, and all around okay guy.

< homepage currently off-line due to change of ISP; back soon >

[Randy Zimmerman]

My guess is that the small piece is gaining so much heat that the plate is
melting rather than burning. If you have to turn as you cut tilting the
torch in the right direction would be difficult.
This is where a plasma machine shines. The other alternative I see is a
nibbler.
Randy

[Cathy Morgan]

I remember having this same problem for a while. I use a 000 tip like
yours, with acetylene at about 5, and oxygen at 15. This works for 16 gauge
to 12 gauge (about 1/8") which should cover the thickness you're using. Try
playing around with some cuts that don't matter - on scrap pieces. I think
doing that finally gave me the feel for how to do it to get full cuts.
Sometimes at first I had to move the torch forward and then move it back a
bit to clear the cut I'd just moved beyond.
Rather than pounding them out with a chisel, you could just go back and
recut the parts that melted back together.

--
Cathy Morgan, Morgan Sculpture
iron and mixed media vessel forms

[Gary H. Lucas]

See if you can get a drag tip. The end is rectangular and has three steps,
one rides on the metal, the center has the oxygen, the highest has a single
preheat flame. A friend of mine cut thin steel with one all the time, it
was the only tool he had, I was amazed at the results.

Gary H. Lucas

Brad Heuver wrote in message <7l0g2c$d...@drn.newsguy.com>...

[Cathy Morgan]

Thought of something else I might have changed, that made this work. Have
you varied the distance between the tip of the torch and the steel you're
cutting? Try it on some scrap pieces and see if that makes a difference.