Technical Body Filler Basics

Excellent thread.

 

Thanks for sharing your knowledge @K13. This thread has a lot of useful information.

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Sorry I missed this question. If you use decent filler there should be no need to do this. This is back to the old mentality of using fillers when they were hard to sand and didn't self level well. The biggest concern would be breaking the bond between the filler and the metal as it won't be fully adhered to the metal until the filler is completely cured. If you are needing to remove enough material that a cheese grader is needed you are using lousy filler or applying way too much in the first place.

 

I’ve see guys slather filler and it looks like they frosted a cake and post pics of it.

Then there’s a squad of guys following and saying ohhh great job.
You damn sure gonna need a cheese grater to get anywhere doing things like that

 

Great information, my question is what is life expectancy of cream hardeners, I have some tubes that the cream looks gritty, time to throw in garbage? Thanks for info

 

18 months from the date of manufacture is about the limit for the life span of hardeners. They degrade over time and lose their strength so even though they may still be hardening the product they will require more and more to properly and fully cure the product over time. If they have become gritty then they are definitely garbage.

 

Thanks for the info, another question, I have epoxy coated some pedal cars after they were acid dipped, is it ok to use bondo over epoxy paint for repairs or should I strip area down to bare metal?

 

Just scuff the epoxy with 80 or 120 grit and you'll be fine.

 

Thank you for the help

 

Those that do their filler work over epoxy. How do you handle areas you sand through the epoxy. do you recoat with epoxy further work?

 

Some people must use POR15 filler because apparently it adheres best to rust.

 

i have started using more ice and less filler due to ease of app/ prep . is this good or should filler be used as a base for strength/stability .and is app .best on bare metal or on primer or sealer ?

 

That all depends on if it’s sanded off a high spot or not. High spots is what ruins the day.
If you just got distracted trying to sand out an imperfection in the filler that really needed filled any way not sanded,,,
Or if it’s where the metal, epoxy primer and filler feathers out. In this case you’re finished and scuff up the surrounding epoxy and blow a little epoxy on, follow the data sheet and move on to filler primer.

For the other situations, since filler has been done on bare metal for eons it doesn’t really matter much till you knock down the high spots or add more filler.

 

I hope I am not just butting in, can I ask you what the best filler would be to fill floor pan butt welds? Just to smooth things out a bit?

 

On a floor pan I would use something reinforced. Maybe even one of the flexible reinforced products. You can message me if you want specific recommendations.

 

@K13 I primed the fiberglass T body with Shop Line JP202 primer surfacer a couple of days ago and now have found some pin holes that I missed (Evercoat gold filler) and some other "occlusions" that I had missed also. Do I need to sand it down totally down before using filler to "fix" my misses....or do I need to use a dremel to get the primer out? Wish my eyes/fingers worked better

 

You can just sand the surface of the primer and reapply. No need to clean out the holes just make sure you blow the area off well so there is no sanding dust left in the holes. You would probably be better off using a putty rather than a filler if it is just pinholes and small areas needing touch up. It will allow you to sand with a finer grit (180) and will be far less likely to pinhole again.