when i removed the seat support bracket to weld in floor patches i had to drill the spot welds out with something like a 5/16" drill bit. I would like to fill some of that in before i weld it back to the floor. Can i weld in a stainless washer to take up most of that big hole?? is the use of stainless a problem with strength?
http://i189.photobucket.com/albums/z121/vrdanna/restoration/floorpanandsupport008.jpg

Don't you have to use a TIG for stainless/aluminum to get a good clean weld? I am not sure if a MIG will do it....but I have never tried so I may be mistaken.

I know that a tig will definatley weld SS... and I did weld it to carbon steel just to see if I could do it...

in case it makes a difference, i will be using a flux core wire feed. i forgot to include that info.

you can use 309 rod with a welder when u go SS to mild steel or 316L SS-SS there is also stainless wire for mig welders

No - you can not use a flux core wire to weld stainless. To MIG it properly you need to use 90% helium-10% Argon gas and stainless wire. You won't get a good weld with your setup. Just weld in a small patch scrap metal from an old body panel.

glad i checked first. i have plenty of scrap, it will just take a while to cut and shape the plugs. thanks

Vince,
If the holes really are only 5/16", you should just be able to weld them up if you take your time and do a little bit on each hole at a time. I am not sure how well the flux core welders work at this, but my old Millermatic 250 would easily go down low enough to weld the holes up.

bill, i plugwelded the seat suframe mount plate to the floor but it was kind of sloppy looking. i guess it's not that bad though. I'll let ya'll know what i decide.

I plug weld 5/16 all the time. It's the size hole my pnumatic punch came with.
And why are you talking stainless weld for this anyway? However you can weld stainless with mig and stainless wire. I use Co2 for all my mig welding.
It leaves a little soot but who cares, I always grind and clean any way. Doesn't splatter like some mix gases either.

The holes in the photo look way bigger than 5/16" they looked like 9/16"

You can always take a peice of flat copper and hold it behind the hole and fill with the MIG. The weld won't stick to the copper. I use a 3/4" copper coupling from home Depot that I crushed flat in my vise. Cost about 50 cents.

Why SS? Just use mild steel and fix it.

I had a box of washers that are Stainless steel and fit in the hole about right and also was the correct thickness. Bob you are correct, the hole is actually greater than 1/2" the inside diameter of the washer is 5/16. the label on the box is what i assumed was the OD.