what do you do with pin holes after welding patches?

[Jocigar]

I have asked before, not sure anyone wants to own this one.

I'm patching around front window and it came out good, but after I clean up the welds it had pin holes at the seem.  do you guys leave them for primer/filler or keep going back to spot weld, regrind, and repete as needed.

[dougs bs23]

You may be able to just spot over the holes, also if you can back up the areas your working on with a piece of copper to help prevent burn through and dissapate the heat.  good luck, have fun, happy welding

[purple1]

I would think you have a few options. What about brazing or lead? Sounds like you don't want to fill with body filler. 

[Jocigar]

thanks, this area I cant back up.   I hate to go back too many times after I get the patch smooth and straight.... pics

[Giveitawack]

I would lead it

[72cudamaan]

I would lead it

     best choice

[Jocigar]

Thanks all,

I ask the question because I tend to go overboard sometimes. 

I could spend many hours spot welding and grinding (using spot welds as filler) to get it perfect.... or I could move on and leave it for epoxy primer and light coat of filler and forgo hours of work.   

In the end, I want to do the right repair without getting too obsessively critical.

[torredcuda]

You never want to go over seams or holes with regular body filler as it is not waterproof and will bubble up if water/moisture gets in behind it.Whether I can actually see holes or not I do my first coat with a fiberglass reinforced filler or aluminum filler,Marglass,Tigerhair,All metal etc.Lead works just as good also (maybe better) but is more time consuming.

[4 speed fish]

I used mar glass.Strong and waterproof.You will find out how strong it is when you start sanding it.

[Jocigar]

    making progress and learning      thanks!!   

I imagine I should buy a gallon of marglass, apply it after epoxy primer?

Can/would you use this on lower quarter patch panel seam?
(I was thinking the proper way is to lead that seam since it will be ~24" long)

[4 speed fish]

I would use mar glass over any seam.

[johns cuda shop]

If I have any pin holes, I back the area up with a copper plate then fill it up with weld. When you grind be careful not to remove the sheetmetal only the weld. Normally I knock down most of the weld with a flap disc then come back with a 60 grit roloc disc. any area that the grinder didn't clean up ,because of a low spot ect. ect. I sandblast the area before any filler or epoxy primer.

[Jocigar]

 

I used a 120 grit flap disc to finish the area.

I dont know about reloc discs, is there a specific tool they get used with?  they dont look like they fit in a grinder.

-----
THese are the steps I came up with based on reading several threads (may help others) ;

-weld
-grind
-sandblast
-self etch primer
-sand
-apply fiber epoxy
-sand
-apply filler

I am hopefull the process will last a long time and reduce or eliminate the welds showing through the paint on hot days once complete.

[johns cuda shop]

A roloc or DA 80 grit is good for prep for primer ,Roloc is the twist lock discs. I never appy filler on epoxy ,I go on fresh clean metal with 36 grit sanding marks. If you dont want the weld to show thru, I would either Tig weld the area or use panel glue . (see pictures)The reason why is the Mig weld is a (hard weld) unlike the Tig weld which is soft. The mig weld will expand differently in the sun than the surrounding metal. It shows up mostly on dark colors ,anywhere there is direct sunlite or long mig weld line (like quater panel skins, ect . If its a small patch on the car it may never show thru. There is a lot of ways to skin a cat . Epoxy is a wonderful product and sticks to clean metal free from all paint ,rust,and weld scale, clean the sanding residue and dust from the metal with metal prep or similar products before prime.l I prefer 80 grit before epoxy for the primer to bite into ,but everyone is different.

[jimynick]

I agree with John and you can use the panel bond for a seam sealer ( I am) and it works great. Just like welding, cleanliness is next to godliness for any of the methods.