ATM building a computer controlled grinding lathe (pictures)

[alphasig@mail.usa.com]

Since my other less conventional ideas have been soundly shot down, I have been thinking 
about grinding a large glass mirror using a computer controlled grinding lathe. The lathe 
will be relatively easy to construct, a block diagram can be found at 
http://www.ShirtsOfWindsor.com/mirror.gif
Basically, a carriage moves back and forth carrying a grinding tool that moves up and 
down. Half of the mirror rotates under the tool head.
For feedback I will sacrifice a computer mouse which will be taken apart and geared 
directly to the threaded rods. Normally these have about 350 points per inch of 
resolution, but I will increase the gearing ration so that it is considerably higher 
(will 1000 points per inch be acceptable?). I will have one axis of the "mouse" track the 
carriage position while the other axis tracks the tool height.
This seems to me to be an excellent fall/winter project that will enable me to create 
mirrors of almost any shape and size I like. I will be able to computer design my optics 
to minimize all aberrations and then grind the mirror to precision.
I assume someone on the list has thought of this before me and has experience with this 
and I would greatly appreciate any comments.

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