Making some progress. Milled the groove in the lower plate that accepts the hinge. The tool is a cobalt 1" diameter, 6 flute, center cutting ball end mill. Best speed was about 1250 rpm and a 30" per minute feed rate. A little higher than I expected, but below those speeds, it chattered quite a bit and the finish wasn't that great. The tool really wanted to cut. We took out from .035" for the initial passes to .010" for the final pass.
The final groove depth was 0.156 or 5/32". I had students do some calculations to figure out what was the best depth to give the hinge the most rigidity without being too deep and limiting space between the plates, or limiting the angle to which it can be opened. Calcs showed rigidity increases significantly up to .150", then only marginally past that. Here's the description of the problem I handed out, in case anyone wants to run some numbers. I'd be interested in what you come up with.
http://wiki.team1640.com/images/8/82...te_Problem.pdf
Also put two 1/2" holes in the plate that match the slot spacing in the mill table so we can bolt it down directly if we need to.
http://wiki.team1640.com/index.php?t...1_151216-1.jpg
http://wiki.team1640.com/index.php?t...1_151216-6.jpg