[BIG DOG]

What grit should I use on the bare metal before I epoxy primer ? I have been told to primer right over the sand blasted spots .But I also read somewhere that there can be particals of sand stuck in the metal. So I was just going to hit everything with the sander but I was wondering what is best .I see lots of people say 80 grit but I also believe that I have read 320 grit ???? Is it possible to make it too smooth so the epoxy will not grab the metal ? Also is there something easy to sand the bottom of a car with ( lots of contours and bends) like a 3m wheel or something like that? Mostly all bare metal now just needs to be ruffed up.
Thanks

[Grit54]

i have always had good luck using 180 grit, the 320 does it to smooth ,,,,for me anyways when i really need to find out if i'm wrong i have a friend that has a body shop so i call him,,,and so far no bad results,,you can also use your search engine and checkout the custom painting sites those guys also very helpful

[OneMoreTime]

Spi recommends the 80/100 grit for their epoxy and I can tell you that SPI epoxy fills those scratches just fine..On the bottom floor boards and such I just use my 4 1/2 sander grinder and get all the high spots I can and then use a Roloc to work out the small spots as needed..Sometimes you will need to do a bit of sandblasting to get into the final small areas..Dupont Starblast seems to be working the best for the guys I know..

Sam

[BIG DOG]

What is a Roloc ?........

[OneMoreTime]

Roloc's are little small sanding disks..they come with an arbor that you chuck in a drill motor or air motor..they are about 2" or so in diameter and great for getting into the smaller spaces..they have a plastic screw on the back to attach them to the arbor..you will need an arbor and some of the disks..good thing to have on hand when doing body work..

Sorry dId not realize that folks did not know about those..http://www.bakerpbe.com/catalog.php?...01&descr=roloc there you go where you can get them..

Sam

[duallybuster]

At my hotrod shop I do the majority of the metal work. I use a 120 grit 7 inch flap wheel on a grinder to metal finish with. I get the the metal to a almost mirror like finish then send it over to the paint shop for refinishing.

[baddbob]

Don't sand with anything finer than 180 for sure, and the paper needs to be changed often at that grit level. 80 grit works just fine IMO and provides the best texture next to sandblasting. 80 grit scratches in bare metal probably compare to 220 grit scratches in bodyfiller if that makes sense- the softer the material the deeper your scratches will be. Make sure you clean the metal well before applying any primer. SPI's waterbased wax and grease remover is some awesome stuff for this purpose. Clean untill you see no more discoloration showing on your wipe off towels. Cleaning sandblasted surfaces can sometimes be a PITA and I usually blow the area off with compressed air to dislodge and abrasives then go over it with W&G remover then when dry I give it a light scuff with a red scotchbrite and compressed air to remove any towel fibers that were snagged during the wipe down.

If the surface is really rough in texture and towel fibers remain on the surface after cleaning and not removed before primer is applied thay can cause corrosion problems down the road. What happens is the fibers get primed over and just show as dirt which most think is no big deal but when sanded the fibers become little wicks that absorb moisture and allow the moisture to reach the bare metal below the primer. This happens a lot on heavy equipment, bridges and other structures but not as much on autos where there's more attention to detail-nevertheless something to consider during the cleaning operation. Bob