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Posted by Private on May 5, 2008, 1:55 pm
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> On Sun, 4 May 2008 18:10:55 -0800, "SteveB"
>
>>When there is a lot of porous spongy glop on the underside of a flame cut
>>that takes a lot of time to grind off and dress?
>>
>>Too much what? Wrong speed? Help me.
>>
>>1/4" thick steel, 4# propane, 20# oxygen 00 tip.
>>
>
> Way to many variables here. But one that I haven't seen posted yet
> is how clean is the metal. If you want a clean cut the metal will have
> to be clean. It's pretty much impossible to cut rusted metal without
> slag with a cutting torch.
>
> Next is the accuracy (can't really think of a proper term) of the
> oxygen jet. If the jet is a nice linear flow that stays small for a
> long distance (say 3-5" from the torch tip when depressed away from
> the metal) then you've got it right. If it gets turbulent a short ways
> from the tip then there's part of the problem.
I think the word you are searching for is 'clean'. Anything that disrupts
the clean flow of the cutting jet will cause a dirty cut. Tip cleaners
should be used often but very carefully, the motion must be straight in and
out as any side pressure on the tip orifice will make it bell shaped and
cause it to behave more like a gouging tip than a cutting tip. If the tip
has a damaged orifice it may be necessary to file it shorter to remove any
belling of the cutting orifice.
Check the condition of the tip by looking at the side of the flame with the
cutting valve open, the cutting jet should be a thin dark line in the center
of the flame and free of any turbulence or feathers out to the side of the
jet, or a jet that gets wider as the distance from the tip increases. A
simple, plain and dark background will make the flame and jet clearer and
more visible.
Lack of oxygen pressure can cause incomplete steel burning in the cut and
lead to excesive slag. Check the surface of the cut, the striations on the
cut edge should be square and straight, any curving of the striations can
indicate lack of pressure or excessive travel speed. The guage may be
defective or the hose obstructed or undersized. 20# oxygen seems a little
low especially if the hoses are long or undersized. Too much pressure is
wasteful and will consume excess oxygen, but will not degrade the cut. I
like a large hose with a short, smaller and more flexible whip on the torch.
Unsteady hands can cause a rough cut and excessive slag, get comfortable,
make a practice movement to check for binding or dragging hoses, and keep
the torch as steady as possible when cutting.
> Last is a tip for getting rid of the slag. If you'll take a standard
> hammer (not a chipping hammer) and hit along the corner where the slag
> is you can usually pop most of it off. If you insist on grinding then
> grinding along that edge at a 45 deg angle will be much more efficient
> than trying to grind it flat. The slag is only stuck along cut edge.
A 3-4" wide piece of old planer blade or similar welded to a heavy handle
makes a large chisel that is a good tool for removal of slag, just use it
flat on the bottom of the cut plate and slide it towards the cut and
underneath the slag.
A proper cut with a CLEAN tip will cause almost no slag to adhere to the cut
edge and the little that does will be very easy to remove. It should almost
never be necessary to use a grinder to remove slag. In general, any need
for grinding is caused by a dirty or oversized tip or lack of cutting oxygen
pressure.
Always remember that with OA you are burning the steel and not cutting it.
You are NOT melting the steel and blowing it away, that process is ArcAir.
Good luck,
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>that takes a lot of time to grind off and dress?
>
>Too much what? Wrong speed? Help me.
>
>1/4" thick steel, 4# propane, 20# oxygen 00 tip.
>