Originally Posted by
HimyKabibble
No matter what you do, the bearings at the business end of the spindle are going to carry the bulk of any side-load, and the one at the other end will be lightly loaded, unless you're working pretty far away from the chuck. In fact, most of the time, the side load on the rear bearing will almost certainly be dominated by the belt tension.
You might also consider using a pair of angular contact bearings at the "front", and a radial or deep groove bearing at the "rear". This is a common configuration for spindles.
I'd suggest putting a "labyrinth seal" on the front, to keep swarf and coolant out, then use shielded bearings, to help keep the grease in place. Positive pressure really should not be required.
I would second the suggestion to find an existing spindle, it not the whole headstock. It'll be cheaper, quicker, and very likely better, than something you could build yourself. Even some of the Chinese ones are not bad.
Regards,
Ray L.