I'm a mediocre self-taught machinist, but I can usually make parts that *function* as I would like for prototypes, etc. For production work, I use local machine shops. My favorite shop went out of business a couple of years ago, and now I'm stuck. They used to make some cylindrical parts for me turned from black delrin. They had a very nice matte finish -- almost as if it had been etched or tumbled, but I don't *think* that was the case. I hadn't needed any more of these parts for awhile, but now that I do, the other shops tell me they don't know how to duplicate the finish. The owner of the first shop is no longer available.
So, does anyone know how to do this? I'd also like to get the same matte finish on turned black ABS parts. My experiments with different grits of SiC sandpaper, with and without oil or water, have gotten me a little close, but still not the lovely, even, original finish. I still get this little bit of whitishness (sp?)to the surface, as well as little "hairs" of plastic. Also, the sandpaper loads up pretty fast.
For the ABS, I've been thinking about using a very dilute solution of acetone and water or acetone and alcohol after the sanding. Pure acetone dissolves ABS quickly, leaving a very shiny surface after it evaporates. My thought is that the dilute solution might wipe out the hairs without dissolving the bulk material much.
Thanks very much for any advice you can provide.