Don't recall seeing any instructions, mind you when I find the bits they will have been kicking around for so long that if there were any they would have gone walkabout.

I have fitted these to a few things and can't remember having problems but then again i may have adjusted any play out.

I fitted a set to a Taig mill, they go nearly straight on because these things work on 20tpi screws.
They are just an encoder that counts based on 20.