So you want a cutting spindle basically.

Have you thought about a round belt drive as used on the old engravers

Tony at lathes.co.uk supplies the belts made to measure

Something like this in the attached poor quality picture
Click image for larger version.  Name: Spindle.jpg  Views: 300  Size: 18.2 KB  ID: 3388

Very quiet and can run all day this is from a Taylor Hobson i was going to mount it on my mill for engraving, but i might get a water cooled spindle instead, it will be clamped in the middle part


Criticism i looked at your machine build and you really should protect the ballscrews from dust ingress.

Phil