New Conversion Startup

[kNucklBustr]

I have a 11x26 chi lathe. Very similar to 9x20. This will be a working machine in a nasty environment. Tolerances are .003", .005" non-critical.
Where do I start? Off and on reading this forum, utube, etc and some things dont make sense to me.
What senses where the x and y is? I dont see DRO scales on some build threads.
Why use a belt, instead of the servo motor mounted direct to the screw? To save space?
Why use a coupler between motor and screw? I read some claim they have zero backlash from ballnut and screw, but then use a coupler. Makes no sense to me.
I think the first item to do is mount the screws and servo motors. Is there anything else involved? switches, sensors that go along?
Do the screws/ballnuts come in kits? thrust bearings, bearings,etc.

Am I posting in the correct forum for these questions?

[doorknob]

What senses where the x and y is? I dont see DRO scales on some build threads.

DIY lathe conversions for machines of that size sometimes use stepper motors to drive the axis positions. Stepper motors are typically run "open loop", meaning that there is no feedback to the controller to indicate the axis position, other than home and limit switches. The controller starts from a known position and then counts steps in either direction to determine position along the axis (taking into account the motor's steps per revolution rating, the amount of microstepping used by the controller, if any, and the pitch of the leadscrew).

If the conversion uses a servomotor instead of a stepper, then typically an encoder attached to the motor shaft is used to keep track of the shaft rotation (along with switches and the other factors mentioned previously).

Why use a belt, instead of the servo motor mounted direct to the screw? To save space?

Some conversions that I have seen use belt drive to change the motor orientation (to save space). Others may use a belt drive to modify the speed or resolution from the motor's original characteristics.

Why use a coupler between motor and screw? I read some claim they have zero backlash from ballnut and screw, but then use a coupler. Makes no sense to me.

Some people use Oldham couplers to compensate for possible axial misalignment between the motor shaft and the leadscrew, without affecting the backlash.

[kNucklBustr]

Along w/the YCL1126 lathe I also have a G5966 mill, see for pic.

The 1126 has a 110v 3/4hp 1ph motor and is on 110v line. The G5966 has a 220v 1hp 1ph motor and on a 220v line. I guess a 220v could be run to the lathe if needed, but rather not.
I decided to edit this post because I read about motor speed control driver. This seems it could be added in the future. Need to keep it simple

Would it be in best interest to keep both motors AC for future use of computor speed control driver?
This gets confusing.
Mill w/220v 1hp 3ph motor>VFD 1hp input 115v/220v 1ph, ouput 220v 3ph
Lathe w/220v 3/4hp 3ph motor>VFD 1hp input 115v/220v 1ph, ouput 220v 3ph
or
Mill w/220v 3ph motor>VFD input 220v 1ph, ouput 220v 3ph
Lathe w/90v-180v DC 2.6hp motor>DC motor controller

Ed