Welding Tips and Tricks

Hi Tig-ers,

I put this in the New member section as I am new here BUT I think that this is a better local.
I am an antique car restoring enthusiast. I have a Miller MIG & a Miller TIG welder; each 220 volt. I am replacing the floor boards that are new 16 gauge steel. MIG has been used to tack and fill several gaps between old, rusty and the new steel.
My question is: Can I TIG weld over the MIG welds to fill in remaining gaps and craters ? Will TIG stick to MIG? Any suggestions on electrode and wire?
Thanks,
Bruce

Tig will allow you to remelt tacks & suchlike as you get to them to leave a continuous bead if that's what your trying to achieve - but I would keep with the Mig - there is really no cleaning action with Tig & pure argon & it hates any contamination of any kind - welding old sheet metal with all the stuff it accumulates is just asking for porosity & a heap of other hassles - the Mig will tolerate a fair bit of this & still leave a good weld - at worst grind the tacks flat first if you want to weld over them.
Just my opinion - some guys seem to love to Tig everything even when it does'nt seem the most efficient way.

When I do floor boards or something like that I will clean the best I can with out thinning the metal to much .then when I weld the seams I weld with spot welds,like pull the trigger for one second then move the gun to the edge of the spot pull the trigger one second then move .kinda stack the spots intill it's a long bead sounds like it takes a lot of time but its better than grinding a crappy one down . The weld ends up a lot flatter because you can set the welder at a lot hotter setting . And if there's a spot that is to hard to get to clean once you get the first spot it seams to let the heat have a little more time to burn off paint between spots .
Maybe manual pulse?
Once you get the hang of it they look pretty good, I will try and get some pics

Ryan

Thanks for the replies.
The old metal is rusty and thin. I am afraid to sandblast for fear of making it even thinner. I have the Miller 140 at a very low setting. I still burn thru trying to bridge gaps where the metal rusted thru and fell out leaving uneven butting of new and original metal. I try to wire brush as best as I can but it's still not very clean.
Bruce