The adhesive bond of epoxy to the filler far outweighs the mechanical bond. The main reason for 80 grit DA on metal is to give the epoxy a solid mechanical bond to the metal (in addition to the adhesive bond of the epoxy to the metal). FIller doesn't need anything coarser than 80 grit.Outlaw said:If im using filler over the epoxy, I always felt I needed more than 80 grit, but I am not experienced like a lot of the members here. Im guessing filler likes more than an 80 grit scratch, but if your applying epoxy first, the chemical bond makes up for a finer grit? I am also under the assumption the chemical bond is superior to the mechanical bond but again, thats just how I have interpreted what I have read on this forum. I dont always interpret thing correctly, lol.