Simple lathe question

I have a lathe I would like to convert but I really don’t feel like dealing with the motor/spindle.  I know I won’t have sfm etc .   But threading…..
if i put two encoders on the spindle rpm/postion . 
can I just set the lathe to the rpm I want matching what I programmed it to and Linuxcnc will handle the timing todo single point threading ? 

LinuxCNC needs two things to do spindle synchronization (single-point threading): spindle speed and an index (once per turn) signal.

The index signal is required so LCNC knows when to start the tool axis moving.

Spindle speed can come from:

• Separate encoder connected to spindle
• Encoder already on the motor
• Home-made encoder attached to spindle (slotted wheel and sensors, toothed gear and a sensor, etc.)
• other devices I can't think of at the moment

Index signal can come from:

• The spindle encoder if it has a built-in index signal
• Separate 'device', like a proximity or optical sensor that is triggered once-per-revolution.
• A second/third sensor on the slotted wheel (see above) and an additional once-per-turn slot
• There's also a 'missing-tooth' configuration available in LCNC, where a software component running in the background keeps track of the encoder wheel pulses, and if it sees a missing pulse where one should be it interprets that as the index pulse.

Did that answer your question?  It's not very specific, but I/we don't know anything about your hardware.

Speaking of which, why are you reluctant to "deal with the spindle/motor"?  Most spindle/motor combinations aren't terribly difficult to get under LCNC's control.

It’s a gear driven lathe and I just don’t want to deal with variable speed , and frying the motor controller etc . Already destroyed a mini lathe motor control board lol. I had made an encoder for the mini with two wheels and two optical sensors. One had like 60 slits and the other had 1 so I under stand that .

For me just turning the spindle on manual and hitting cycle start Is fine for the needs.

I wasn’t sure if I would be able todo threading and Linux CNC would just adjust the feed to compensate for the spindle load etc .

Yes - with that encoder & index signal LCNC will adjust feed while threading to compensate for spindle speed variations.