TIG sheet metal tips

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Hey everyone, I'm gearing up to start welding bicycles which usually have tubing in the .02 - .04" range. So I've grabbed some 22ga sheet metal and started practicing some t, lap, and outside corner joints to get the hang of things. I've run into a few issues so I'm looking for some general tips from you pro's. I'm using .040 filler and tungsten at ~65A, and getting mixed results. Starting the pool is very difficult, stay to long and it blows through - to short and I can't get a good puddle flowing. My other biggest issue is the end of the joint, near the edge of the metal - if I maintain my puddle it'll always blow through, if I back off a bit, the bead goes cold. Any general tips would be great!
Reply:1-fire off on the rod, not the sheet. Let the rod's melt fuse to the sheet2-65 amps is waaay high3-if you have pulsing on the machine, that can help. Currently for thin steel, steel, aluminum or SS, I'm using a pulse rateof 3-5 PPS, with very high peak current. This method repeatedlysees less total heat input than other parameter settings and one'smoving very rapidly on the joint. Quick, subtle movements of the torchhelp to agitate the puddle.-Presumably you're using 2% thoriated or ceriated tungsten?Point ground along the length to a long taper, with tiny blunt onthe end?-You may need to try .020 dia. tungsten, if things just don't cut it.-torch is (-), ground is (+)?-and the ground lead connection is nice, bright, and clean?....Everybody thinks TIG is so easy, but I don't know why they say that.Blackbird
Reply:Great stuff Dave! I will add a couple thoughts: Be sure to drill a vent hole into the other tube sections. Obviously, the crank journal, and seat tube don't need venting. But the upper and lower frame spars and the rear tubes for the back wheel/ dropouts will need venting or you will blow it out every time. Be sure to get a super tight fit up. A gap will be inviting disaster. Lastly, use a copper heat sink. Some copper pipe would be really trick for this. if the frame tube is 2", then get a piece of 2" copper pipe, and cut it ???say 8" long. Then, split it down the middle. Use a simple leather strap to hold it on the frame where you will weld, and hold it back 1/4-1/2" from the weld. Aluminum tube would work in a pinch also. It will draw some of the heat away, and allow you a bit more workability on your welds.And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:The following is more for tubing than sheet.Make sure your fitup can hold water or the edges are going to melt away fast. Let both edges of the joint pool together before adding filler and running the bead.If your torch angle is too relaxed the filler will ball up before you can feed it into the puddle.Smallest tung I use is 1/16", lanthanated as of late. Filler is .035, but will be going slightly bigger when this batch runs out as the .035 disappears quickly.I don't pulse and keep the dial @ 70-80 amps, but the pedal is not floored. Leaves some headroom if needed.Move around the joint with distortion in mind. Not only head tube, seat tube, or bottom bracket distortion (which will wreak havoc on facers and chasers) but each weld will pull the frame out of alignment. I typically move around a joint in eigths, less if I don't have a good view of the joint.My first "frame" was a front triangle replacement on a Salsa. I replaced each tube individually while keeping the others in place to maintain geometry. Most of the welds were cold and ugly as hell, even blew through the seat tube and used a gusset patch to keep it out of the trashcan. But it came out straight and still ride it today.Keep at it, it'll eventually all come together.
Reply:Thanks Dave!I gave this a shot last night and had some better results. I had my max amperage set to 65 before - although it was never floored. I took it down to 40A, which seemed to give me a little more room for error on the pedal which helped. I am using 2% thoriated, which I ground to a longer point last night - that also helped a little bit. I have a pulser, but since I'm a beginner I'm sort of reserving it for when I feel fully comfortable without it. One thing I'm still confused about - you said "fire off on the rod, not the sheet". Does that mean I should start my arc directly over the filler to start a pool flowing? Sounds clever.. As for the end of the joint (edge of the metal), I was having issues blowing through. I think I may have figured out a way to get by that by adding a little extra filler to my last dip, then backing off the heat while pushing that extra bit to the end of the joint. Although I'm not sure if that's a good or bad way of going about it.Thanks again!
Reply:sporkedtospec: Thanks! I familiar with lugged/fillet frame construction so I've got the miter/fit down pat. I've got a pound of .035 I was planning to test on some old bike tubing after I figure out sheet metal. Out of pure curiosity - what advantages do you see using a 1/16th tungsten over .040? Originally Posted by sporkedtospecThe following is more for tubing than sheet.My first "frame" was a front triangle replacement on a Salsa. I replaced each tube individually while keeping the others in place to maintain geometry. Most of the welds were cold and ugly as hell, even blew through the seat tube and used a gusset patch to keep it out of the trashcan. But it came out straight and still ride it today.Keep at it, it'll eventually all come together.
Reply:Originally Posted by uid_bThanks Dave!I gave this a shot last night and had some better results. I had my max amperage set to 65 before - although it was never floored. I took it down to 40A, which seemed to give me a little more room for error on the pedal which helped. I am using 2% thoriated, which I ground to a longer point last night - that also helped a little bit. I have a pulser, but since I'm a beginner I'm sort of reserving it for when I feel fully comfortable without it. One thing I'm still confused about - you said "fire off on the rod, not the sheet". Does that mean I should start my arc directly over the filler to start a pool flowing? Sounds clever.. As for the end of the joint (edge of the metal), I was having issues blowing through. I think I may have figured out a way to get by that by adding a little extra filler to my last dip, then backing off the heat while pushing that extra bit to the end of the joint. Although I'm not sure if that's a good or bad way of going about it.Thanks again!
Reply:Thanks again Dave!I'll keep practicing tonight, the biggest hurdle I've come over so far has been to just learn to calm down. Steady breathing and, for me, counting a rhythm 1..2..3..4.. seems to help tremendously.
Reply:You probably would be better ahead to just start practicing on thicker material--like 16 gauge, to get in the swing of things.     As you might begin to see, there's all kinds of little things one can dowhen dealing with thin stock.    First thing is learning how to throw the heat and run the puddle-consistently.That in itself can take a whole lot of practice.I don't think many guys are really excited, when doing bench work-as you comment.It's more like just approaching the work, figuring 'let's see what happens' and the workshows you, very quickly.Last edited by dave powelson; 06-08-2010 at 09:09 PM.Reason: additionBlackbird
Reply:you might want to consider silver solder for tubing that thin.
Reply:Originally Posted by boatbuoyyou might want to consider silver solder for tubing that thin.
Reply:sheet metal is a pain, I would say it's one of the harder areas of welding as fit up is so critical and its hard to maintain a puddle. talking about sheet, the preferred position is vertical down, with a very shallow torch angle about 15-30 degrees. it feels like your torch is pointing parallel to the sheet. This is so that the heat hits the surface instead of trying to penetrate straight down. fit up is critical, we generally tack every 2-5 inches, but for beginners more is better.  Also running higher amperage is good.  Or what I should say, if you dwell to long at very low amperage you heat up the base metal so much that when you finally get  pool going you are prone to blowing right through. If you run a little bit higher but MOVE MOVE MOVE and pick up the torch speed it's much easier to skim the surface and control your penetration with speed and torch angle. I was a sheet metal welder for a good portion of my welding career, and one place I worked at only had thumb switch torches, we would set it around 55-65A for 18 and 20Ga we didn't do 22 ga in normal work.  About blowing through.  IF you suspect it's blowing through or it starts keyholing, BACK OFF. either run the torch backwards or skip ahead, but whatever you do, don't dwell because once you bust through it's a nightmare to fix.  Most of the welding we did was without filler, which is an acceptable practice for sheet below .100"  Filler tends to slow people down from the dipping which makes it more likely to blow through, running without filler is considered easier. AS mentioned fitup is key. you tack every 2-5 inches then come back with a sheet metal hammer and beat on the joint so that they are in physical contact.  a lot of good advice in this thread, sheet metal welding is one of the hardest forms of TIG welding in my opinion because the tolerances are so tight compared to what most people are used to.Welding EngineerCertified Scrap Producer
Reply:Thanks Metarinka! I've definitely noticed the importance of fit-up. Sure wish I had a shear  Anyone know of some tips for cutting the stuff without one?
Reply:Get one!  for 22 ga, you can get a hand powered shear on the cheap. that or if you have a plasma cutter you can use a rail or template to get straight lines.Welding EngineerCertified Scrap Producer
Reply:A plasma cutter's definitely next on the list. My mother even has one!