proper sanding

[SinCrisis]

HI i just have a quick question,

I'm modding an old compaq case and the paint on it is pretty thick, do i need to sand all the paint off before repainting? like get to the point where i can see the steel?

[slaveofconvention]

Not at all - you CAN if you want to - but if you go that far you'll need a special etch-capable primer for bare metal. There's no reason you can't just sand it down a little to clear the surface of any little imperfections and provide a key for the new paint to get a grip on. A layer or two of a decent build primer, sanded between and after coats will help you get a REALLY smooth finish....

Something else to consider is that the case may well not be painted at all - it's very likely it'll be powder-coated - in which case sanding it to bare metal will be a HUGE job....

[SinCrisis]

well... uh, ive been sanding it by hand and it has been super difficult. In some parts im at the bare metal and other not...does this mean i need to sand it all to the metal and use that special primer? its only been the door, the rest of the case, well now i know better and wont sand it all the way, however parts of the door are already at the bare metal so should i just sand it all the way? Also what is powder coated? some parts of the door i sanded down way fast to teh metal, even before i realized i was sanding the metal and other parts are taking forever to sand down.

[nevermind1534]

I used a palm sander (orbital) on my powder coated case, and it wasn't too bad. I either used 80 grit or 60 grit sandpaper.

[SinCrisis]

ive been using some aluminum oxide fine sandpaper from m3. it doesn't tell me grit on mine. It just says fine, good for metal and wood. Does this mean i am sanding everything to the bare metal before i can add primer and paint?

[nevermind1534]

You don't want fine sandpaper for heavy sanding. For that, you want coarse, or, at the very least, medium.

[SinCrisis]

Well, i have sanded it to smooth already, i just want to know if i need to finish sanding this to the metal now that i have roughly 1/7 of the door sanded to the metal?

[slaveofconvention]

I'd suggest stopping where you are - put a couple coats of primer on, and rub them down with the fine paper -ideally, with soaking wet "wet'n'dry" and see how it feels - not looks - be your own judge - if you think it'll look ok and the primer appears to be holding properly to the case then start with colour

[SinCrisis]

whats wet'n'dry? do i just wet my sandpaper? or pour water over the primer coat as i sand? or is it a product...?

[SgtM]

Wet/dry sandpaper is sandpaper that can be used wet or dry. Here's how I would proceed. If you have most of the panel sanded already, you might as well go all the way.

Primer - dry sand with 400 grit. That way your base coat has something to bite to. You don't want the primer to be totally smooth, or else the base coat won't stick.
Basecoat - Dust coat until you get full coverage. Don't try and hog the paint on. It'll run. No sanding necessary unless you have dirt nibs. In which case, only sand enough to get the nibs out.
Optional - airbrush artwork or whatever else you're doing to the paint job.
Clear - after your clear coats are done, wet sand with 1000, move to 1500, finally 2000. Then use some 3M fine cut rubbing compound, followed by polishing compound. Wait about 30 days, and wax with car wax. Waxing sooner will seal in the chemicals that need to cure off and will basically turn your paintjob to gel.

The end result will be a mirror shine with no orange peel. Make sure you follow the directions on the can regarding coat times to the letter.

My latest paint job - http://www.thebestcasescenario.com/f...516#post252516