[TheForge] Thanks for the info: learning to use a cutting torch properly

Fri May 30 00:29:00 2003

Hi Andy; Thanks
RE 1. that's generally about right..a hair more clearance is OK, but as 
you back off, the cut gets wider and the flame velocity drops.
2. Fuel pressure is critical with welding tips and relevant for cutting. 
 With a hotter preheat,  you get a faster start ( important if you are , 
say, cutting a dotted line prior ot bending. Also ,you can move the cut 
faster in  lighter materials, but it's easier to make a mess. Each tip 
size has a fuel pressure range that's right for it.
Oxy pressure is more critical to results and increases with thickness to 
be cut with a given tip size. Each tip size has  it's range of 
pressures.  Too low and you get a slow ragged cut with slag inclusions 
and incomplete penetration..too high wastes expensive oxy at a minimum. 
and requires fast, even  tip travel. Sometimes you can pick up some 
speed by angling the tip direction forward. Using higher pressures and 
laying the tip over almost flat, it is possible to go like crazy on 
thinner materials, but it is hard to control.
Some welders set the fuel at 5 and the oxy at 20 and never change it. 
They get by..sorta. To do good work you need to dial it in.
The preheat is basically there to get the base metal up to hot enough 
that it literally burns on exposure to oxy. That burning ( exothermic) 
supplies the heat to continue the cut. Strictly speaking, all you need 
once the cut is started, is the right amount of oxy. I saw a guy in a 
muffler shop heat a spot on an exhaust pipe, then turn off the acet and 
complete the cut all the way round the pipe using just the oxy......Pete

Gladish Family wrote:

>Great batch of info- thank you all who replied!
>I've been buying steel at a shop that does a lot of cutting jobs on thick
>(1" to 5") stock- torch cuts that look almost like laser...made me ashamed
>of mine. Have seen some awful plasma cuts here and there too, so I suppose
>that's not a magic bullet either...
>Couple of further questions:
>
>1) I usually hold the torch so that the cones are just barely off the stock-
>is that the right distance?
>2) When you say correct gas pressure, do you mean fuel or oxy, or both? Is
>one more critical?
>3) Always thought that 35 ox was about right for general work- is that what
>makes my cuts slaggy on the far side?
>
>Andy Gladish
>
>
>
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