O/A weld problem

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I'll start by saying I've got a Lincoln MIG that's been used a lot for car  body work, and an old Victor O/A setup (acet. B bottle) that's been used primarily for heating/cutting.  I've not had a lot of experience, or success, with welding using O/A.I've been trying to make some  3/16 O/A butt welds with limited success.  The largest tip I have is a #2--which the chart says is a bit small, and it does seem like I don't have enough heat?Rather than spend $60 for a #3 tip, the Airgas guy suggested I could enlarge the #2 tip slightly.  I probably don't really need the #2 tip, as the MIG will (just) handle that size range, but is this a bad idea?The other question concerns acet. bottle size.  Have read on this forum about the 1/7 rule, and apparently the B bottle is marginal, even for the #2 tip?  Again, Airgas guy says, if B bottle if full (it's over 300 psi now) shouldn't be a problem for limited amount of welding?Thanks for your help.
Reply:i would not touch the tip. you want to learn something, first make sure the problem is not the equipment ,,you'll never know if  you tamper with the tip..look online for how to adjust a torch.. that might be yer problerm.. thers a site called tmtechnologies,  (tm=tinman) about metal working,, i rememebr on  there is a description for how to set up a  torch..you can bring the acet and ox up in steps to get more heat...i dont think a welding tip will get you in trouble with the 1/7 rule, usually need a rosebud for that..300# of acetylene is close to full i believe...
Reply:Dont drill the tip, as mentioned. Its more than just a hole, and judging by your post you dont have the experience or equipment to even do it. However I may be wrong on that, so please correct me if I am. A # 3 should be in the $20 range, not $60, unless airgas has you suckered into buying victor brand tips. The Radnor branded tips for your particular handle will work just fine. I could write a book here on how you should get started, but fortunately there ARE books already published, some even for free! Go to www.esab.com and look in their literature section. I dont doubt the airgas guy told you to drill the tip, quite frankly I havent met one welding store guy that knew OA welding.
Reply:I just got my O/A setup yesterday, so I've been looking into this stuff.  Apparently the 1/7 rule has recently been changed, and is now 1/10 for intermittent use, or 1/15 for continuous use.http://www.thefabricator.com/Safety/...le.cfm?ID=1457Your acetylene B tank is a 40 cubic foot tank, so you shouldn't be drawing off more than 4 cubic feet per hour.According to this page (http://www.hoopersupply.com/tipchart.html ) a Victor #2 draws between 5-10 scfh, so you're marginal already with that tip.This all sucks as I just bought a setup with little burglar bottles, and only have a 10 cubic foot tank.
Reply:Just thought I'd post this reference in this thread as there was some talk about acetylene tanks and how to tell if they are "full". I learned a great deal from this and related threads.http://weldingweb.com/vbb/showthread.php?t=17620Also curious about the timing of this, but I just priced a #3 tip (to basically solve the same problem as the OP) from AG for my Victor setup  and it was around $43....not sure if Radnor makes an equivalent...MikeMiller Dynasty 200DXHypertherm PowerMax 45Victor OAIR CompressorLots of blacksmithing tools and other fun toys meant to creatively disfigure, reshape, manipulate and join metal.
Reply:that explosive issue is why more people are going with propane /o2 set up, there are no issues on how fast you use propane...
Reply:Thanks for the replies.  I have read a good deal about welding but as you know there's often a large gap between books and what's in front of your torch.      Fairly sure I know how to correctly adjust the torch.I said I was trying to do butt welds--maybe because of other threads I'd been reading--though what I meant was lap joints.  Don't mind buying a larger tip if that's what I need.  Is it?Thanks again.
Reply:Yes, larger tip. Laps and Tee welds require a larger tip yet than the equivelant butt weld. In the case of the old OA welding books, you pretty much can follow them word for word, there is no magic. Propane, useless for fusion welding steel, not relavant to this topic, acetylene has advantages much greater than energy content that makes it suitable for fusion welding of steel. Draw rate on the "B" marginal....maybe. I have a feeling the witdrawl rate was changed more for those people that like to "push the limits", and provide a further safety margin. Years ago, a limit would have been set that meant "exceed this and boom", now you see 2:1 safety factors....which kind of fits in with the new ratios. If you can afford it, get a 3 and a 4 tip. There IS a reason they have different sizes, and what they sell now is nothing compared to the original offerings in the '40s. Victor used to make "half" sizes. Smith used to make every number, not just the odds, Harris had "half" sizes. On and on. Have fun!