I got to do a bit of work on the fixtures last Friday. To be more precise, I machined the main pocket and reference geometry:
This fixture is the first of two, which holds the raw stock in place for the first operation. When it's complete, the major outlines of the vise will be visible and ready to be mated with the second fixture. I tested the geometry with my prototype vise:
Unfortunately the pocket is just a little too small for the stock I have on hand, because I forgot to take into account the tolerances that the supplier provided - the stock is -0/+0.125 inch. It's not a big deal; I can bring the size down with the mill or with a band saw. It is a bit annoying, though.
After testing the fixture, I took my prototype to test on my MDX-15. The fit is amazing! It's pretty mind blowing how well this thing indexes. There are a few opportunities for design improvements, but overall I'm pretty satisfied.
To help improve the surface finish on the next prototype and the fixtures, I ordered some new tools from Tormach.
They include some new collets and holders, a new 1/2in carbide finishing end mill (which is gorgeous, by the way), a thread mill for cutting the threads used by the fixture clamps, and a set of high polish aluminum inserts.
These inserts are specifically designed for cutting aluminum. You can see the difference when I put one of them side by side with the general-purpose insert:
High-polish tools with sharp edges work well in soft materials and provide a better surface finish, but they're more liable to chip when the going gets rough or if you shock load them (or drop them). I'm hoping that a 10-pack is enough to keep me supplied for a while. This week the plan is to tackle the rest of the features on the first fixture, and start making a new vise. Then I can finish the second fixture and test it using a new part.