CNC converson of a 626 Turret Mill in hte UK

Well after much struggling to find information, I finally find this
group which I'm sure could have helped me in the earlier stages.

Hello everyone. I'm starting to realise now that there are others
trying to achieve what I am. Didn't feel like this about a year ago.

Would like to give a bit of an introduction, so please skip down to
the questions if you start falling asleep.

For a bit of background, I've always appreciated good machined items
which I'm sure we all do (don't see enough of them these days) and
bought a lathe about 3 years ago. Its just a 7x12 but I got the bug
once I'm made a few bits for my hobby (RC Models).

About a year ago I bought a milling maching from Chester in the uk.
Didn't really know much about milling then, but always intended to
go the CNC route. The states seems to be great for this, lots of
CNC ready kits or mills available, but here in the uk it really
isn't easy, and I didn't really want to think about shipping
something that weighed half a ton across the ocean. Wanted
something big aswell but didn't want a 3 phase boxford taking up
half my garage).
It seemed to me that there was little between the boxford and the
micro (seems strange there is this gap) but my sights have always
been above what a micro could do. Who knows perhaps I might want to
mill a new rocker cover out of billet for my car - wanted that
option and the micro's seemed so limited. I found a machine that
seems to be a rare size - and I'd be interested in anyone telling me
exactly what machine it is, as I've never been able to find the
machine its cloned from although it must be a clone. It was an
asian import. 626 turret mill from Chester Tools Uk. I'm very
pleased with it.

http://www.chesteruk.net/626turretmill.htm

Just getting it in the garage was a challenge and I'm dreading the
time I move house. Anyway didn't take long before I realised the
limitations and the human error (yes made loads of mistakes) that
hand cranking had to offer. Time to convert to cnc which I think
would make a very capable machine (this thing eats through ali whith
my roughing 10mm cutter) I have so far obtained 3 gecko drives and
3 very nice stepper motors. Again this all came from the states as
I've found nothing here unless you wanna spend big money. I soon
discovered that the leadscrews although pretty good in my machine,
would have to be replaced and managed to find and get machined 3
ballscrews (actually only tackling the x and y just now) for what
seems a very good price considering they are being machined (£300
25mm x 900mm, y300mm).Should turn up next week and I can't wait to
see how the motors perform with these (I've had some skipping and
stalling with the leadscrews when trying to reduce backlash).

-------------End of boring bit------------------------------------

Onto the questions which I'd appreciate any input on.

1) The z axis, how have people tackled this with a similar machine?
I've ruled out driving the fine feed wheel due to the heavy preload
spring that pushed the quill up to take out he backlash in the worm
gear and rack and pinion. The set of ballscrews I have purchased
includes and 8 inch 15mm ballscrew which I want to use. I am
thinking remove the wormdrive altogher along with the preload sping
and somehow fix to the spindle directly to the ballscrew (there is
an adjustable stop that comes out of the front of the spindle which
could be used). It would need to be at the front of the machine but
mounting wouldn't be the easiest and there isn't much room for the
pulley, but I think it can just about be done. Just wondered if
anyone out there could offer any advice or other options on this.

2) Getting my y axis ballscrew into my machine is looking like it
could be tricky with the ballnut in place. Its preloaded, but I've
been told can be removed and replaced by using a mandrill. Don't
really understand how this would work or exactly what a mandrill
is. Can anyone explain please?

Thats about it. Nice to meet you all and thanks for any responses.

Lawrence.