CNC Lathe

backyardengineer wrote:

Thanks again for the advice, starting with the parallel port doesn´t sound so bad afterall.

There is a lot to recommend starting there.

As for the spindle encoder, can Linuxcnc do this switch (from precise positioning to tachometer/rough positioning) at a given rpm? -> so the parallel port can keep up ? If not, a Mesa card would make a lot of sense

You could just let it lose position at higher speeds. I had a lathe that worked that way (parport).
It re-synchs to the index at the start of each threading pass, so it's not a huge problem.

I recently added missing-tooth index to the encoder counter, so you can do position and index with a single parport pin. (For your stepper-positioner I think you would need to work open-loop, though)