Newbe choosing motors

Hi all,

after much thinking, I've decided on going CNC with my lathe (kind of
an 8x14). I've already purchased two geckodrive g201, and plan to use
the turbocnc software.

What's driving me mad is the selection of the motors. The numbers
I've done are:

- with a leadscrew of pitch 3mm, 3 cm/sec seems good enough top
speed, so 10 turns * 200 steps/turn *10 microsteps/step, so 20,000 Hz
seems ok (ok with both g201 and turbocnc).

- for the Z axis (the heaviest one, so I understand), 300 oz-in may
seem near the correct torque value, maybe a little low (?).

So my questions are:

- is 300 oz-in a good aprox value for this size of lathe? Is there
any good method of choosing this value?

- should I gear-down and get cheaper motors? If so, to what limit?

I cannot see the implications, apart from the frecuency needed, of
this pair of parameters.

Thanks in advance for any help!

Cheers,

jaime