hi, i am trying my hand at body work, i try to read as much as possible on the forums before making a move to try to prevent amateur wobbles. I took my project to metal on the rear of cab to replace a section of metal, then epoxy primed with mp170 and started applying filler, i was block sanding the filler down and the epoxy is sanding off as easy as the filler? I thought the epoxy was supposed to be tough and very hard to sand? Obviously i am not sanding specifically at the primer but i am hitting it trying to level the filler, completely green to this work so any suggestions and comments are by all means welcomed and very appreciated

I have the p sheet for the epoxy nd it shows a 30min dry time for recoat and it says after 3days it must be scuffed and reapplied to continue, but does not give a cure window for filler?!?!?!? just called parts house where i got it, they just quoted the p sheet to me lol

 

What grit of paper are you sanding the filler with?

 

i hit the high spots(my great application) with 80 grit and once its knocked down i go to 150 to try to level it then 220 finish up and try to feather it

 

Epoxy primer is very tough, but needs to sand easily. Also when sanding, whether it's filler or primer or blocking, always sand in an "X" pattern to avoid flat spots and let the paper do the work, never push down as this will sand lows into your bodywork. As for the sanding grits, I use 80 grit on filler, then go straight to 220 and finish with no finer than 320. Lay two coats of primer on any filler then three more coats over the whole vehicle (or panel if it's just a repair) before blocking. Never, ever sand with just your hands, always use either a block or a sanding pad to keep your fingers from digging grooves into the panel. To get into contours and curves that blocks won't fit, use whatever you have that will fit, I've used sections of rubber hose, paint sticks and whatever else is handy to fit where you need to get into. Patience is essential and always think it through if you're having trouble with something. Hope this helps, Jim

 

80 grit's gonna take epoxy off. Its not granite. It is the best for bare metal though.

 

The purpose of the primer under the filler is to create a good bond between the metal and the filler. As you level the filler you will expose bare metal (either as a high spot or "perfect edge"). Then you simply apply more primer on the bare (and filler) to create another good bonding surface. If you're taking out mild ripples or minor dents, you may have to do the filler/primer/sanding multiple times. Always block sand as mentioned above. Never put filler on bare metal as the alcohols in the filler wick moisture and will seal a tiny bit of water against your bare metal.