My first official project, this scope mount rail was fabricated entirely on my Grizzly mini-mill. I worked off the specifications posted on www.biggerhammer.net, and also used my Bushmaster V-Match flattop AR-15 rail as a secondary reference.
Fabrication
I started with a piece of aluminum bar stock approximately 6 inches long, and milled it square.
Then I milled out the four notches for the mounting rings and test fit it on the M96 receiver before continuing.
Next I milled the sides down to the proper rail width, and cut the groove underneath the actual mouting rail area. I could have removed the bottom portion entirely instead of cutting a groove, but I left it alone for two reasons: 1) to provide a clamping surface for future milling operations, and 2) to provide rigidity in the finished mount.
After the groove was cut, I tilted my mill head 45 degrees from vertical, clamped the workpiece sideways in the vise, and cut the bevels for the mounting rail. This was a simple operation made tricky by the limited table travel in the Y axis. I had to cut the long bevel at the rear of the mount, then flip the workpiece around and cut the short bevel at the front from the other side. It sounds complicated, but it wouldn't have been a problem on a larger mill. I didn't have a good way to measure the bevel, so I cheated a bit by using my dial caliper to measure the width of the 45 degree plane on my Bushmaster, and just eyeballed it until I got close. This isn't a very critical area, so it turned out fine.
Next I used a 3/16" end mill to cut the mounting grooves. I admit that I cheated here as well. Instead of doing the math from the diagram, I simply used my dial calipers to measure the width of the material between the grooves. Since my cutter measured about .185", and the groove was .206" or so, I would make one complete pass through the material at full depth. Then I would advance the cutter about 20 thousandths and make a complete pass the other way. Then I figured I had to advance my cutter .185 + .175 = .360 to start the next groove. The Grizzly's X handwheel is graduated from 0 to 62.5 thousandths, so I simply made six full turns of the handwheel, stopping at 60 and resetting to 0 each time. It probably would have been neater to do six full turns and then back up .015, but then backlash would come into play, and I didn't want to mess with it. Anyway, my little method worked out fine.
All I had to do next was to drill the mounting holes. I placed the mount into position and held it there while using a transfer punch (exactly 1/4" size) to mark the center of the hole. I carefully drilled the two holes out and that was that.
I did put a slight bevel on the front of the rail by clamping it in the vice at a 45 degree angle facing upwards. Then I used the bottom of my 3/4" end mill to cut the bevel.
I didn't bother with exact angles here, I just wanted to break the sharp front edge of the rail.
Finishing
I cleaned up the burrs and broke the sharp edges with a file. I removed the remaining layout fluid and WD-40 residue (I use WD-40 as cutting fluid) with brake cleaner.
Then I took it over to my blasting cabinet where I gave it a matte finish with aluminum oxide abrasive. Another shot of brake cleaner and it was time to paint it.
I used my very last bit of Brownell's Teflon Moly paint that I salvaged from the clogged-beyond-repair aerosol can. I applied it with my airbrush, let it dry for about 30 minutes, and fired up the old toaster oven I'd paid $5 for at a garage sale. I baked it at 300 degrees for about half an hour and pronounced it finished.
