Following on from this thread I have thinking about building a DRO based on rotary encoders and the software available over here.
The biggest problem I can see is how to mount the encoders to the axis (assuming 3 axis knee mill for now). I have read about using fishing line to rotate the encoder, and someone even used a mouse mounted to an axis and used the mouse' own encoders for the DRO.
What I have in mind would be similar, I am thinking along the lines of a rubber wheel attatched to the encoder, and having the movement of the tables turn the wheel, therefore rotating the encoder. Obviously there are some issues with swarf or the rubber wheel not gripping efectively (either not enough grip or too much to damage the encoder). But what do you guys think?