Milling

Feb 10. Finished turning the last of the adapters and set about milling flats into them. The first two took half an hour apiece. I was attempting to end-mill the metal to a broad, smooth surface, but as I was completing the second, I realized how much cutting surface was going unused on my bit. I turned the work parallel to the mill and used the side to cut metal away. That's the ticket.

Clamp the carriage down tight after adjusting the tool holder's position and angle (make sure the work is parallel to the axis of the cutter). Only the cross-feed and the milling attachment's feed provide degrees of freedom. Take 35 ticks of the cross-slide (half a turn) with each pass of the work up through the spinning flutes. Back off 5-10 ticks while returning the work to the bottom of its travel to prepare for the next cut. Cut only with the work being fed into the flutes, not when the work is moving in the same direction.

I am using my largest mill and spinning it at my second highest speed. A drop of 3-in-1 oil applied between mill and work after contact has been established makes all the difference. Now it takes 2-3 minutes to set up each piece and another 3-4 to cut a face. I have only six adapters left to cut down and am saving them to take a running start at the project tomorrow.

Next: drilling the adapters. Installing set screws in the truss tube adapters, dry fitting tubing for the mirror support truss. Drilling the frame and tapping mounting holes for the truss tubes. Milling the inside of the frame to accept the mirror cell. I think then drill holes in the center frame and level it with respect to the mirror frame by adjusting the adapters at one or both ends of the mirror-truss tubing. Repeat for the corrector cell frame and truss.

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Text & Photos by David Cortner
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