Threading with A B phase only?

The only connection to your computer is the ethernet cable to the Mesa card. Pretty sure you can do modbus comunications from the card too, however I just used the normal spindle interface 0-10v.

Andy what do you think is your maximum and average total current draw by your setup? My workshop is on a 20 amp fuse (I could fit slightly larger but it already causes problems when my wife is in the laundry room!) - it is on a ring circuit covering workshop + downstairs sockets that has absolute limit of 32 amps. The inverter (240 single phase to 240 three phase) is a heavy consumer of amps and so the one I have is only 2.2kw because input limit for this inverter is 19amps. Hence I never had any machinery of more than 2.2kw until this one arrived. I can happily run the 4kw motor at half power by inputting standard 2.2kw parameters to the inverter and accelerating gently, but I am worrying that the total draw of the system when two 1090 oz NEMA 34's (max draw at 5.6 amp per phase) are running, plus the transformers from 240v ac to 24v dc , plus the 24v motor brake, plus general circuitry and lighting and suds pump is going to be too much. What do you think and what do you think is the lowest power Stepper Motors I could get away with?

I don't think you need to worry about the steppers. They are drawing maybe 6A, but at about 5V. (Voltage across the windings, not the same as power supply voltage). Just not in the same class as spindle motors.

I put in a 50A (240V) supply to my workshop, but I really don't know what the actual peak draw is.

Ah thanks for that!

Regarding choice of pulleys for the 1090 oz Wantai stepper motors (which are now on their way!) for this Encomat project, can I assume you reused the existing ones for the main carriage leadscrew, but for the Cross slide leadscrew what do you recommend for the driving pulley and for the driven pulley - number of teeth and pitch? Many thanks, Adam.

Yes I modified the original for the Z axis, and bought a pair of HTD5M Aluminum Timing Belt Pulleys off of ebay. I pulled the graduation dial off the cross slide handle and bored one of the pulleys to lightly press on the handle. Then i drilled and tapped for 3 cap screws to secure it.