I know that during the first year or two of the restoration I’ll be doing TONS of bead-blasting. For the uninitiated, it’s basically sand-blasting except they don’t use sand anymore (very unhealthy). Industrial blasters use mostly aluminum oxide which is pretty sharp and abrasive stuff. Hurl thousands of bits of it at a hundred psi or better and you’re gonna do some damage. Not only does it remove rust and paint but it can actually cut into the metal if you aren’t careful. There are other media you can use that are more gentle on the surface such as glass bead or walnut shells. I’ve used a big industrial blaster before and it’s fun but I really wasn’t ever happy with the amount of damage it did to the underlying part, even when I was being careful. It’s a shotgun to kill a fly, most of the time.
So, I picked up a desktop-sized blasting cabinet designed for dental or small parts work (model 2100 VAB for the curious). It still uses about 100psi but the grit it throws around is much finer, we’re talking down to 50 micron! That’s the equivalent of 240 grit sandpaper. You spray through a little “pencil” and control it with a foot pedal, it can recycle the grit or you can switch to fresh “clean” grit for, say, a final pass. The next thing I needed was some rusty stuff to practice on. That was nearly a problem, without outdoor storage (I’m an apartment-dweller) there isn’t a lot of rusty stuff around here, but luckily my boss at work has a carport that breeds rusty tools and he loaned me a few as test subjects.
Here are some before and after shots with my new toy.
Very happy so far. As long as the rust hasn’t pitted very deeply, the tooling marks from when the parts were made still show up. These have a roughly similar amount of rust on them as the worst parts of the aircraft. Of course that rust has accumulated over a longer period of time. No predicting what I’ll find once I start cleaning stuff up, but at least I’ll know my blaster isn’t going to do any unnecessary harm.
Oh, and in case you’re wondering, after blasting I finished with a scotchbrite wheel and then some metal polish on a buffing wheel. The surface left by even 50 micron grit is quite rough and unpleasant to hold. This is with aluminum oxide, I recently got some 50 micron glass bead so that will be the next experiment.