sandblasting rear brake calipers, what do I watch out for? Options

[914 RZ-1]

I am rebuilding my rear brakes. I've taken everything apart, cleaned them with Simple Green and am currently soaking the parts in Evaporust. However, I might need to sandblast them.

1. Anything I should know before I proceed?
2. What to plug/tape up? I'm assuming all holes and machined surfaces?
3. What about the area in the caliper where the piston goes?
4. What blasting media should I use? I have some dull aluminum oxide I've used several times.

I've looked on the 'Net and found a few tidbits, but nothing specific to 914 brake calipers, so I thought I'd post here and see if anyone had any experience, tips and advice.

Thanks!

[Sycolyst]

I glass beaded mine covering all the internal openings. I then wiped them with lacquer thinner and blew them out with compressed air. I took 1500 grit sandpaper to de-glaze the piston bores. I painted mine with caliper paint and installed all new rubber and rebuilt them. They came out great. Take your time, it's not a hard project.

[PatMc]

I glass beaded mine covering all the internal openings. I then wiped them with lacquer thinner and blew them out with compressed air. I took 1500 grit sandpaper to de-glaze the piston bores. I painted mine with caliper paint and installed all new rubber and rebuilt them. They came out great. Take your time, it's not a hard project.

Depends...are you going to have the castings replated or leave them bare or paint them?

If replating, don't mask anything, blast everything. Assuming this is a relatively small home based blasting setup and not some 300 PSI deal where you can blow holes through things, nothing will be damaged or hurt at all. Aluminum oxide or glass bead or whatever media you choose will work fine. All calipers at the commercial level rebuilders are blasted with steel shot, and nothing is masked....and if they don't leave them in the blaster for 3 times as long as they should, there is zero damage to the casting or any machined surfaces.

If you're not going to be replating the castings, then I'd mask off anywhere that plating still exists...like on the mating surfaces between the halves. I'd also follow up with a wire brush on a drill or grinder to polish the bore and seal groove as best you can after blasting, then coat the bore/seal groove with a good caliper assembly lube (containing rust inhibitor) ASAP. The caliper will still likely be short lived without any plating or surface conversion treatment of the bore (when my customers request painted calipers, the castings get a zinc phosphate treatment for at least SOME protection and better paint adhesion).