manual to cnc questions

I am probably going to get a 12z and gradually mod to cnc. I have already modded my G0704 with the stock screws and am getting sufficient accuracy for the one off parts I make, but I need more beef as I usually work in steel. I would like to (at least initially) use the stock screws on the 12z and stick with steppers like I did on the 0704. Don't see a need to have high ipm for rapids but I may want to take some big cuts. Would it be reasonable to use the same nema 23 570 oz steppers at 2:1 or 3:1 (reduction) ratio for the x and y? and 4:1 on the z? At this point I think I would prefer to not counterbalance the head, and I plan to stick with the stock fixed speed motor.

The nuts have a poor backlash arrangement and will not keep a low lash. The bronze is also soft so will ware vary fast.

I would think you could direct drive the X and Y as long as you don't put the table all the way to one side with the vice sticking out. The table is really large for the size of the Y carriage so it has a lot of over hang.

The head is about 250 pounds and the stock lead screw has a fairly high lead so it takes a huge amount of force to lift it. The larger steppers cost more than a servo and the full size Geckos servo driver cost about the same as the stepper drive so I would get a servo for the Z and you might as well get a ball screw too. The stock lead nut has a lot of friction.

I have 4 or 6 extra servos I could let go for cheep. I also have a 110 tooth MDF T5 pulley made to fit the Z, also a 100 tooth PVC T5 pulley. The MDF worked better than you would think it would.

With the 570 oz steppers and the servo setup going to ball screws should not require new drivers or steppers. The 570 are a little under sized but just might work OK.