What do I need to add to turn threads

I am about to rebuild my shopmaster eldorado which was converted to CNC several years ago, but has had issues the last couple years. I havent been able to figure out the issues and decided it will be easier to start from scratch and build it myself.

When I do this I want to add a reluctor wheel or whatever is needed for LinuxCNC to read RPM and be able to turn threads.

Any suggestions on what to get and how it should be integrated? And advice on setting up the config?

Or links to info on this topic, i have had no luck finding anything relevant.

Thanks, Can you share a link to get me looking in the right direction?

would this work if i made a sensor disk with a single slot/hole?

www.ebay.com/itm/1x-Slotted-Optical-Swit...f:g:W-QAAOSwyZ5Ungn9

ElDorado is a 3in1 mill/lathe I am using steppers to drive the axis. Everything I have read confuses me more so I thought i would ask here. I found some threads with this type sensor being used, but not much info on how.

okay, i didnt find those documents, i will do some reading

The lathe is run from a series of belts, the only gears we the original threading gear set up which i never used.

here is what im dealing with
drive.google.com/open?id=10P6yM2mA6uabLPSY8lxa_EZj_yo1x0sl3A

and this is the controller mess i need to redo and clean up
drive.google.com/open?id=1lWs5Ii5x4ljl0JxhRheHjJOPeuD7fFSzcQ