This page is page is devoted to my current ATM project a 4.25" F13 ish Classic Cassegrain with optical window. In the near future I'll add some pictures of the window blank and the splitting of the secondary in half as it is too thick, but for now all I can put up are some pics of me coring the primary mirror at the end of fine grinding.



In this photo you can see the way I reduced to spindel speed of my drill press to some thing sane in the context of cutting glass. Basically I made a pully out of massonite and plywood that is 33cm in diameter which gives me a final spindle speed of about 120RPM. This is plenty slow enough for cutting holes (trepaning) upto about 3" in diameter above this you got to go even slower.

The hole saw that I'm using was made from a can style hole saw with a bimetalic rim, what I did was I cut this toothed rim of and cut some small hacks into the resultant tube with a hacksaw. These groves are to distribute the grit around the cut during the cutting process. I don't have a good photo of the cutter that I used, but I'll take one when I cut the core out from the front when I done figuring the mirror. In the following photo the cutter is the red object. The guy opprating the drill press is your's truely.



Oh BTW this arangement is definantly not OHSO Approved so _if_ you decide to do this be very carefull a breaking belt really hurts and this arangement can take your fingers without a by-your-leave! Oh BTW those observant few of you out there will have noted that I'm not waring safety glasses, this a BIG no no in any workshop, so do as I say not as I do!

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