Hi Walt,
I kinda do this stuff for a living so bear with me *G*
1. Metal prep is paramount...impurities promote bubbles which can blow through thin material....get it clean!
2. Practice! Develop you settings and technique on scrap material of the same type and thickness...
3. Fit! If you follow the legion of butt welders here, make sure that fit is TIGHT......Personally, I'm a flanger and lapper but a lot of guys here feel that promotes future rust...
4. Technique! I prefer to use straight Argon, .025 wire and the stitch welding panel on my Lincoln SP200 AB with the arc volts in the 12-14 range and the wire feed at around 100ipm....the timer is set at 1.5 seconds on/ 1 second off...
Remember, a big machine like mine just gives you more flexibility but doesn't mean you can only weld thick stuff...you can simulate this on your welder by manipulating the trigger...just watch for the puddle to solidify and put your next one down at the leading edge of the previous one...the trick is to start the weld on the area where the gap is straddled...I sometimes use a forehand technique as opposed to trailing to just spill the puddle over to the gap area...
When metal gets down in the 18-20ga range, I switch to the TIG welder for more control.
5. Backup! On thin material, it's often helpful to use a copper or brass backup....after tacking in the patch, the backup can either be clamped, supported or riveted in place....I've even used copper water tubing smashed flat in a pinch.....the trick is to make sure it contacts the back of the weldment to prevent burn-through....the copper carries away the heat rapidly and supports the back side of the weld...
6. Take your time! With many welds, you only have one chance to do it right and the actual welding time is brief....so, prepare, practice and think everything out ahead of time...then go to it!
Good luck!
Pat
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