help with tig welding

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hey guys im new at this i just bought a used miller maxster 200 st and i was traying to weld some exhaust tubing 1/8 thick the machine was set at 40 amps using argon gas and the tank was seat to 15 pounds of pressure if that is said correct. my ploblem is that when i weld two tubings that the puddle is really small and what it actually does is burn thrue the side of the piping how could i make the puddle bigger and not burn thrue the pipe while joining it .also i dont have a foot pedal just regular small tig gun is said correctly again thx any help i would really appreciatted
Reply:40 amps is way to low for 1/8". You should be up closer to 90-125 amps. Also 1/8" is some HEAVY exhaust tube. That sounds like pipe. I'd guess the tube is probably closer to 18-22g. Generally a good starting point would be 1 amp per .001" so  18g would be about 50 amps, 22g about 30 amps. Seeing as you are blowing holes at 40 amps the thinner tube sounds closer. With tube this thin you won't get a big puddle. Thin tube is not the easiest to learn on, especially without a pedal. I'd suggest you look into getting a pedal or hand controler. This will let you regulate the heat as you weld. When it looks like it's going to drop thru you can back off the amps a bit and let the puddle cool and then keep going.If you can expand one piece of tube and slip fit it you will have a much easier time than if you just try to butt join it. Also with thin tube you can lay your filler on the work and start your arc on it and then wash the puddle onto both pieces to get the original puddle going. After that you can fill as usual..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:If you're punching through at 40A, then I suspect you are either welding thin material as suggested by DSW, or you are sitting on the spot for a long time, as you are not used to welding the material yet. That is common at first, to go way too slow, or to 'swirl' the torch trying to make a good looking puddle. You likely have the torch with the dial on it, and those are good for steel once you get used to them. But to start, they are a bit tough. My suggestion is to get a puddle formed quickly, and move faster, just for practice. No filler; and no swirling or anything. Just burn a line, and see how you do. Take pics, and show us, we can help more effectively with pics.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.