Oxygen/Acetylene Welding

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All,I recently decided to try my hand at oxy/acet welding.  I have a small portable victor kit.  I have on it a #2 tip.  I have my pressures at about 5 PSI oxygen & 5 PSI acetylene.  I am attempting to weld together two pieces of 1/8" hot rolled 2" x 2" tubing. I have beveled the edge of both pieces 45 degrees.  Admittedly they do not butt up against one another perfectly. (very small air gap)   I have 1/16", 3/32" & 1/8" copper coated filler rod which I picked up at my local welding supplier.  I even rented a technical video on gas welding to learn the basics.  The problem I am having is that after I (try) and heat both surfaces up uniformly, right when I expect the metal to form a molten puddle, instead it just 'explodes' or 'pops'.  It's not my torch going out, but like the metal itself (I believe).  I'm about 95% confident I am adjusting to a neutral flame as described in the video I rented.  Any help as to why this is happening would be greatly appreciated.Steve
Reply:First, I'm assuming you have clean material (no oil, rust, paint etc..). That said, it sounds as though you have too much heat -- drop the pressure down to 3 PSI for both -- and/or use a smaller tip. Don't leave the blue cone of the flame too long in one place. As soon as you see the metal become "plastic" (not molton) start moving the torch in a very gentle swirling action to help start to move the puddle along. Also, try regulating the heat by moving the cone of the flame in/out a bit and not touch the pubble all the time -- that way you can control the puddle better.Just keep practicing -- it'll come together with a few days of continuous practice.Good luck!!Last edited by goodfellow; 12-08-2006 at 09:07 AM.
Reply:Maybe you are getting the tip too close to the material, and knocking it out. Try a slightly acetaline rich flame , then alternate to a neutral flame. Keep the tip out of the metal. Goodfellow is dead on with swirling the torch tip. It keeps the heat in check, and spreads it evenly.
Reply:If you are new to oxy-acetylene, you might also try just getting a bead going on a piece of flat stock; not welding anything together, but getting a little puddle going and pushing it along while you add filler.That way you lessen the number of variables (yeah I'm an engineer), and you are just figuring out how the heat works instead of dealing with a round tube (harder) and a bit of a gap (also harder). Once you train your brain in how the metal behaves when it becomes plastic from heating, *then* you can move on to worrying about joining stuff.just my 2 cents,John
Reply:Runchman, gives great advice. Get some plate or sheet & play around making a puddle & moving it around  a bit. I was beginning to think there werent anygas welders here.,
Reply:I had the same problem with the same setup.  I am a beginning welder, but consider the following.The portable Victor kits typically come with an "MC" 10 cuf acetylene bottle. The flow rate on a Victor #2 is 10cuft per hour at 5psi.  The 1/7 rule on a 10cu ft tank is 1.43 cu ft per hour.  Using the that setup at 5psi you exceed the 1/7 rule by 700%I called Victor, the tech agrees. Portable kits are for very, very brief bursts.He mentioned risk of regulator damage and flashback. Several times.My gas supplier verified this.If you do the math on that 10cuft bottle, only the very smallest tip at the lowest PSI squeaks into the 1/7th rule.Yes, you can adjust the flame down, but then you reduce flow and risk flame starvation and that is a leading cause of flashback.  If your torch is heating up noticibly, STOP.  I switched to larger bottles, got some smaller tips and haven't had a pop since.  The tip stays cool, and the heat stays where I want it.  I don't have to worry about overdrawing the acetylene, ruining regulators and burning dow n the building...as much
Reply:Thanks for all the great advice.  That last suggestion was the most interesting and most disturbing ha ha.   I can upgrade to the next size tanks for only $75 so I think I'm going to do that.....just to be safe. I will also try running a bead on flat stock for some practice. Also a great suggestion.  I guess I was just a little impatient.  I have an old Sears AC arc welder, maybe I should set that up.....
Reply:Originally Posted by swamper8Thanks for all the great advice.  That last suggestion was the most interesting and most disturbing ha ha.   I can upgrade to the next size tanks for only $75 so I think I'm going to do that.....just to be safe. I will also try running a bead on flat stock for some practice. Also a great suggestion.  I guess I was just a little impatient.  I have an old Sears AC arc welder, maybe I should set that up.....
Reply:just a bigger tank means more run time