TIG: Filling in 1/4" holes in 20 gauge stainless?

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Hi, I am new to TIG welding and have been practicing running beads with no filler on 16 gauge steel using a Lincoln Precision 225 with 1/16 2% thoriated tungsten.I have a big piece of 20 gauge stainless I would like to make into a workbench top (not for welding).  I will glue it to a 3/4" piece of MDF.  I found a guy that can bend it for me so it will fit perfectly and look professionally done.What I need to do now is fix 6 holes that are in the stainless that are about 1/4" in diameter.  My plan was to practice on pieces of scrap until I get the hang of it and then weld up my final piece.Questions:- My plan was to punch out some circles out of the same material on a starret punch and weld those to fill in the holes, does that sound right or should I just build up the holes without any filler stainless?  Should I use filler rod?  I have 1/16 308L filler rods.- I have looked for videos on technique to fill holes in thin stainless but I can't find any.  Do you guys know of any?- Any tips on the setup of the Lincoln 225 to get me started?  Should I use the same 1/16 2% thor I have been using?  Cup size?  Gas flow?- At the shop where I will be welding there are 2 Lincoln precision 225s.  Can I use the torch from the other one to back purge the weld?  Any tips on how to do that (flow, use the other torch with no tungsten and have some one push the pedal while I weld)?Thanks for your help and I appreciate your patience with my beginner questions.
Reply:Hello jmvar, a better solution might be to use a countersink and prepare the hole edges with it and then screw in some stainless steel flat head screws that are oversize, in other words, they will stick up above the surface and when you grind/buff them off the screwdriver slot will be gone and they will blend nicely with the rest of the surface. If you try to do a weld fill/repair of any sort on that thin of stainless steel you'll likely have some buckling issues to contend with. Just my $.02 worth. Good luck and best regards, Allanaevald
Reply:Originally Posted by aevaldHello jmvar, a better solution might be to use a countersink and prepare the hole edges with it and then screw in some stainless steel flat head screws that are oversize, in other words, they will stick up above the surface and when you grind/buff them off the screwdriver slot will be gone and they will blend nicely with the rest of the surface. If you try to do a weld fill/repair of any sort on that thin of stainless steel you'll likely have some buckling issues to contend with. Just my $.02 worth. Good luck and best regards, Allan
Reply:Remember when dealing with the thin stuff: pulses! Weld. Cool. Weld. Cool.....Be wary of The Numbers: Figures don't lie,. but liars can figure.Welders:2008 Lincoln 140 GMAW&FCAW2012 HF 165 'toy' GTAW&SMAW1970's Cobbled together O/A
Reply:Use a piece of copper or aluminum to back the hole. Filling a 1/4" hole in something thin is easy.Airco Ac/Dc 300 HeliwelderMillerMatic 200 (stolen)Miller Maxstar 150STLMiller AEAD200LE (welding and generating power) Hobart MIG
Reply:It's probably very hard to do w'o the sheet metal bucking and warping. I think a patch could be tacked in by using a series of 1/4 second pulses spaced like 5 seconds apart.Last edited by MikeGyver; 05-14-2014 at 07:44 PM.Welding/Fab Pics: www.UtahWeld.com
Reply:Originally Posted by aevaldHello jmvar, a better solution might be to use a countersink and prepare the hole edges with it and then screw in some stainless steel flat head screws that are oversize, in other words, they will stick up above the surface and when you grind/buff them off the screwdriver slot will be gone and they will blend nicely with the rest of the surface. If you try to do a weld fill/repair of any sort on that thin of stainless steel you'll likely have some buckling issues to contend with. Just my $.02 worth. Good luck and best regards, Allan
Reply:If you really want to try something fun, get a pneumatic hammer and some big *** countersunk rivets. Tack the dog crap out of the patches (with filler) and hop around when you do it. You can weld kind of cold and grind/file off the excess. Or fly like the wind with a normal heat setting. Pulse tig. High freq. I mean there are plenty of ways.