Need a perfect 8mm hole - to ream or bore?

[HankMcSpank]

Thanks guys...I now realise I didn't give enough info!

I've just bought a slug of 60mm diameter ali... it's 100mm long off which I will cut a slab of 30mm mount in my lathe to work on.

I will turn don about half of this workpiece down to leave flange on one side of the plate, which will have a grub screw going through it to grip the stepper shaft (I'll put a flat on the stepper shaft).

Therefore this 8mm hole needs to run 30mm deep through my workpiece. So is it possible to buy a boring bar that would go into say a small 7mm hole and allow me to cut 30mm into the ali?

I guess a reamer would be my best option but they seem to run a bit expensive and I'd need one per hole diameter type (I like the flexibility/flexibilty of a boring bar) ...have I git this right?

cheers,
Hank.

PS to refresh your minds (or show those that missed my first time round of questioning!), here's the bit I now need to make out of ali...

http://img160.imageshack.us/i/14811707.jpg/ - ie the round transparent faceplate in the piccie.