Simple DRO

I just thought of this last night and I am sure some one else has to or it
is already out there but I would like to put a cheap DRO on my Index Milling
Machine and don't want to spend $600-1200 to do it. What I was thinking of
was a simple rotary encoder with a shaft of a special diameter and to use a
wire that is anchored on one end of the movable part of the slide it would
then be strung along the slide wrapped once around the shaft of the rotary
encoder and continue along the slide and the anchor at the other end with a
spring to keep good tension on the wire. The rotary encoder would be
anchored to the stationary part of the slide assy. When the movable part of
the slide moves the wire would roll around the encoder shaft and translate
linear motion into rotary. A encoder with quadrature with 4,000 counts per
rev and a shaft dia of .63662" would give 0.0005 linear travel per encoder
step. There would be a little work coming up with a small LCD screen and a
few buttons and a basic stamp program and controller to run it all.

What do you guys think? Are there some other simple cheap DRO options?

Thanks
Scott

Scott Riddle
sariddle@...