butt head, butt weld.., I need some help |
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butt head, butt weld.., I need some help |
TravisNeff |
Feb 14 2005, 02:09 PM
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#1
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914 Guru Group: Members Posts: 5,082 Joined: 20-March 03 From: Mesa, AZ Member No.: 447 Region Association: Southwest Region |
Hey all,
I have been trying to patch up A/C holes in my tub and having a helluva time blowing holes in the metal and voids around the weld area. I start with tacks in the corners and start tacking around the world in an offset pattern, when I have about 12 tacks in a circle I try to join the tacs. However when I tac, I most always blow a hole in the new sheet metal, or in the old panel. I have the worst time in the vertical position. I have ground down both sides of the panel (and patch) to clean metal. If I am not blowing a hole, only about 50% of the weld gets good penetration, when I hit it a little longer I blow a hole. I have even used a sorta chill bar to back the joint (1" copper pipe squished flat with a bend, suggested by another lister). Also, I am making most of my holes just buzzing a tack, not so much once I have an arc established. I have a Millermatic 175, using .023 wire and Argon/CO2 (about 24lbs pressure when I hit the switch), Guide states I should use #2 on voltage and 50 on the wire feed speed. I have no problems welding lap joints at these settings and it sounds like bacon frying when it does it, so I know I am close. I have gone down to 1.5 on voltage and reduced the wire feed to 40, still no luck. I have expanded my stickout (experimenting with 1" plus down to the 3/8's I normally do). The welds suck. Once I get done and grind the welds down smooth I almost always find a crack/void where the metal joins the weld. Weld, grind, weld grind. I can eventually get it right, fixing each one of the patches once I grind it down. I have tried the butt weld clamps, but the gap is huge, I can get the metal to almost (or actually touch) and hold it in with a magnet. What am I missing? Should I be using metal ready to clean the metal even further, try another technique? I am holding the gun at an upward angle and a touch over to the side (hell I have tried just about everything). |
IronHillRestorations |
Feb 14 2005, 09:38 PM
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#2
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I. I. R. C. Group: Members Posts: 6,719 Joined: 18-March 03 From: West TN Member No.: 439 Region Association: None |
What everyone says about technique is right. Practice with the same kind of metal you are welding on the car, and go ahead and blow holes and weld them up. It's the only way you are going to get the hang of it.
Another thing you can try (off the car first of course) is to run about 3" of wire out before you make your arc. It takes a little bit of practice to get the hang of it, but it helps keep it from blowing holes. I use a copper spoon to weld up holes, when it's possible, but you've got to work on that technique too, so you get good penetration and everything is stuck together well. Makes me think of the first time (20 yrs ago) I tried to weld sheet metal, and NOT with a wire MIG. Had one of the venerable old Lincoln 225's, great for stick welding 1/4" thick or more, but take a small electrode, turn the amperage down, and POW it'll blow a hole through 20 gauge sheet metal the size of a half dollar in the blink of an eye. Oh jeez....wtf....oops did I do that (IMG:http://www.914world.com/bbs2/html/emoticons/sad.gif) A lap weld can be an acceptable repair, as long as the lapped side of the joint isn't exposed to moisture. This is hard to pull off on a floorpan unless the car is on it's side, or upside down. I would NEVER lap weld flairs, I don't car what any body man says. Talk to any quality restoration shop and see what they say. |
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