Doing a CNC conversion on a Clausing 4900 10"x24" metal lathe. Trying to size steppers and drives, but the more I research the more cloudy things get.Tried the motorcalc spreadsheet but don't know if I'm getting anything anywhere close. Here are the known parameters I have come up with so far:

1hp spindle motor
Y-axis will be ballscrew 25mm x 36" long 5mm pitch
X-axis will be ballscrew 12mm x 12" long 4mm pitch original dovetail cross slide
(Y-axis weight load)Weight of carriage+cross slide+ toolholder+X-axis components = approx 40-50 lbs
X-axis weight load (Weight of cross-slide +toolholder etc= approx 20 lbs

looking for decent rapids and ample torque but don't want to break the bank. Looking at Leadshine drives and others of decent quality that don't cost a fortune.

what speed rates should I be aiming for... for rapids? For cutting?

What are pro's and con's of using NEMA 23 versus NEMA 34?

Should I use timing belt/pulleys to gear up or down? and if so how do I determine optimum ratio?

Are hybrid steppers worthwhile? looked at several but seems like limited motor size options on lower cost products. Whats the difference between ones that use encoders and ones that don't? Are encoders necessary for accuracy or are alternatives just as good these days?

What are advantages and disadvantages of digital drives?

I'm open to suggestions as far as sizes, brands, etc. Still haven't been able to wrap my mind around the holding torque specs vs torque needed. Hard to find many specs on some of the motors.

what are others using on similar machines?