OFC
Flame Cutting
There are several adjustments on a torch that control your success.
They can be sorted into two groups according to whether you can do the adjustment while cutting or you have to do it prior.
They are:
1) size of tip
2) oxy pressure ( fuel pressure is generally left constant)
3) amount of preheat
(second group)
4) angle of torch (material under 1/4 inch)
5) cutting speed
6) height above work ( critical for acetylene)
Also remember the number one cause of frustration is a dirty tip.
The variables listed are not hard and fast for each thickness and application.
For example if the tip is too big then the preheat will be too big and the plate will overheat creating a lot of melted slag hanging on the bottom edge. The solution is to pickup the speed.
Excessive speed is indicated by sweeping lines on the edge when cutting thicker materials.
If there is a need to increase the speed of the cut to save time and sacrifice quality then larger tips and more preheat is the solution
Freehand cuts need getting used to. Steady shallow breathing will control movements. A person holding their breathe cannot keep steady on longer cuts.
If you are right handed your left hand should be formed into a
fist and resting on the plate. The right hand should be holding the torch
so that the forward part rests on your fist which becomes a fulcrum. If you
roll your fist the torch will move forward and back about an inch. You
swing the torch with your right hand pivoting the torch on your fist
creating a left to right motion that is a slight arc. You remove the arc by
rolling your left fist. This will give you a cut about ten inches long
before you must reposition.
I don't believe in using any hardware on my torch, however some people
swear by their circle cutters. I have better success with my freehand approach.
I do use a guide bar that is simply a piece of heavy flat bar 3/4 by 1
� inch about twenty inches long. I usually have a short one also about ten inches or less for cutting flanges on beams. The edge that I use to
slide the torch along is rubbed with soapstone. The stuff makes an
excellent high temperature lube so that your torch tip glides smoothly
along. Always make cuts towards yourself when using the bar. You must be
careful however because the slag will be dropping in front of you and it
could get into your boots if you stand too close.
When you start a cut the important thing to remember is to heat the edge
to kindling temperature then move your torch off the edge, depress the lever
and travel into your cut. If you press the lever while you are over the
plate edge the metal erupts with slag flying up at you. The same thing
applies if you are restarting. Heat the end of the cut until red, move back
into the open kerf, depress your lever and move into the plate again.
" Piercing "
If you must pierce plate heat a spot until you have it a red colour then
slightly raise your torch and tilt it slightly. Gently depress the lever
and the slag should erupt and fly up vertically but slightly off in another
direction. If you have the torch vertical the slag will blow up into the
tip and your tip is instantly fouled. If you still want to have a few
friends be careful which way you tilt the torch. The slag will fly up and
out until you manage to blow completely through.