Hello,

i'm just striping down my old 9x20 lathe and getting prepared to convert to cnc.

i'm after some (any) suggestions and pointers with these types of lathe.

i have a couple of main questions.

1, lead screw pitch? Whats good? i have been looking at 4 or 5mm lead I want a reasonable amount of precision, probably more important than ultimate speed as it's not the most rigid lathe in the world.

2, i'm intending to attach the motors with timing belts, any advise on type/matirial? I'm thinking of the steel belted T5 belts at the moment.

3, i see a lot of 9x20 lathes have the ball nut mounted to one side of the cross slide, are their any issues with this? E.g. Racking the slide/angular misalignment or flex.

4, how much torque do i need on a lathe this size? I'm thinking much torque would be helpful for power slotting etc. should i try using a bendy torque meter on the screws to see or will this be pointless as I have brass nuts currently (well its cold in the uk , arrg bad joke).

5, i'm thinking of getting the low to medium price ball screws and nuts to start with to help with getting it together now and to work out any problems then replace with better ones if it's all working out. Are the nut sizes similar between brands etc. or totally different?

5b, ball screw backlash, is it an issue? How much is common on cheeper ball screws? Should i be using double nuts on each axis and pre load them against each other?

6, tool change, whats the best way to go? Can you use multiple tool posts as a cheep option? Or a fount tool and a back tool (either upside down or reversing the spindle)

7, rs232/485 3 phase vfd, brushed DC or BLDC motor?
(This is probably later down the line as i will most likely first set it up with the single phase motor it has currently)

8, reflective spindle sensor , encoder wheel or ? For spindle sync.


any other pointers welcomed.

I'm intending to use emc2 as it seems to support threading and be very reconfigureable.

Many thanks in advance, sorry if it's too many silly questions all at once. :)

Stuart