[digitalis49]

As an absolute metalworking novice but one who enjoys this hobby I have been following this great site for quite some time now and have learnt a fair deal from you all.
For my question, I hope I am on the right page here.

I have been given 3 Nema34 stepper motors, power supply and breakout boards.
The BF20's X & Y lead screw shafts are 10mm diameter.
The Nema34 motors have 13.5mm diameter shafts.

Only interested in doing X & Y for now.

Questions:
1. Your suggestions for pulleys and belts & belt size/length
2. Suppliers of belts/pulleys (any in Australia????)
3. Way to disengage the steppers to allow manual table movement.
4. Should I replace the leadscrews.

I apologise for my ignorance and hope you can help me.
Thank you.

[Max Power]

I would just go direct drive and skip the belts and pulleys myself. A NEMA 34 stepper will be more than powerful enough. I'm using 23s on my x and y. As for the difference in shaft diameters you can simply get a 10mm coupler and bore out one end to match the 13.5mm stepper shaft size. That is how my z axis with the NEMA34 is connected.

As far as disengagement goes, when you power down the steppers they can be turned by hand. A bit of added resistance but otherwise fine. I've got mine with handles still on and it works. That said I never use them. Much easier to jog /MDI in Mach3 then run it by hand IMO.

Yeah as painful as the cost may be, you are best to replace the leadscrews with ball screws. There is an Ebay seller mentioned in many threads that will supply them cut to your needs for less than $200 USD. Some have success with CNC on the stock screws but it is a wise investment.