On Wed, 16 Apr 2014 06:45:26 -0700 (PDT),
wrote:

On Tuesday, April 15, 2014 6:05:44 PM UTC-5, Cydrome Leader wrote:
wrote:

On Monday, April 14, 2014 3:02:24 PM UTC-5, Cydrome Leader wrote:

I finally dug out the $2 garage sale Craftsman (really Harris)



oxy-acetylene cutting torch. It came with a cutting head of unknown size



which I just cleaned out and #7 torch tip.







It passes the soapy leak test when pressurized, and the o-rings appear ok.







I've not used one of these before but have run into a problem.







I set the acetylene until the flame is not a smoky mess. Then I add oxygen



at the cutting attachment valve (It's wide open on the torch handle) then



I push the cutting lever and the flame gets really vicious. When let go of



the cutting lever, the thing goes BANG and the flame goes out.







What might be going on here? I've got a new set of torch side flashback



preventers to attach before I play with this more.







The welding forums go on about how this is backfire vs. backflash and that



the torch is leaking air or the O2 pressure is too low or something is



broken. It's all vague.







I had the O2 as about 10PSI at the regulator and the acetylene around 5.



Not sure if these are correct-ish.







Suggestions?



You probably have 6920 cutting tips (most common) on your torch. Make sure that the tip is clean (use a cutting tip cleaner). Regulator pressure depends upon the tip number that you're using (stamped on tip barrel). See:

http://www.harrisproductsgroup.com/~...onCUTTING.ashx



That looks about right. The cutting tip I have is apparently stamped "1",

so the chart indicates 35-40 PSI for the oxygen.



I did finally unscrew it from the torch head and there are half shiny

metal/half dark looking surfaces where the tip mates with the head. I'm

going to assume this is no good and it needs to be cleaned or corrected

somehow. Links to the photos are below:



the torch itself



http://www.panix.com/~presence/torch.JPG



the mating surfaces of the tip



http://www.panix.com/~presence/tip-seat.JPG

Maybe try cleaning the mating surfaces with some fine steel wool. Check for daylight between the mating surfaces or mark the mating surfaces with a colored marker to see how they seal.
Water based only. NOTHING containing any oil or flamible materials
near oxygen.