No eBay APP ID and/or Cert ID defined in Kunena configurationThe difficulty with a lathe spindle is that it has a big hole in the middle, so you either need an encoder with a big hole, or a belt / gear drive with a 1:1 ratio or to make your own encoder.
The latter can be cheap and effective. You may even be able to use a gear in the headstock if you have any, though you seem to be suggesting that you don't.
The problem with a commercial encoder is that they tend to have a lot of counts per turn. This isn't too much of a concern if you have hardware to count the pulses, but if you are using the parallel port then you need to consider your sampling rate and spindle speed and choose a counts-per-rev to match.
If you are making your own encoder disc then you can choose a slot-count to suit.
If you do buy an encoder, make sure you get on with an index pulse. There are some pretty cheap ones on eBay, for example. (check the part numbers, but I think that is an ABZ encoder, ie three-phases including index)
That's a 100ppr one, you can go higher if you are not using software encoder counting. (if, for example, you are using a 7i76)
