Lathe spindle index only?

I have tried searching but cannot seem to find what I'm  looking for. I am getting ready to convert my little 9x20 lathe to CNC and am trying to find out if lathe threading can be done with a single index pulse only.  Basically I would make an index plat with only one hole in it and use an optical sensor for the trigger. Is this possible in LinuxCNC, and could anyone point me to an example?

Thanks,
John Brannen

An index pulse alone is not enough you also need a pulse train signal like an encoder channel to track the spindle velocity:
linuxcnc.org/docs/html/examples/spindle.html

It has been done (using interpolated position) but depends on very good
speed control of the spindle vs load, since you are essentially "flying blind"
for 1 whole turn.

With the software encoder you would connect the external index pin
to both 'A' and 'index' of the encoder component and set the encoder
component to counter mode.

A small improvement to deal with just one sensor would be to have a 1/2 disk
so you can get 2 counts per turn.

For my 9x20 spindle, I used optical sensors and cut 65 teeth into a thin disk. With two carefully offset sensors I get 260 quadrature counts and haven't had any problems threading 120-150 rpm. A third optical sensor provides the index from a deeper tooth.

I ordered an omron encoder off eBay ($20) that will be a lot cleaner. When I get around to installing it I will probably 3d print gears for a small belt running around spindle and encoder. If you go this route don't go over board on pulses per revolution. 1024 ppr will be more than enough for threading.

The most difficult part of my 9x20 conversion was the modifications to fit a small ball screw under the cross slide good luck!

Thanks for the reply PCW. I guess I will go with a system that has an index and also at least some number of pulses per rev on an additional channel.