Centec 2 ballscrews

[Jonathan]

now that i have me some screws i need to get them machined. i have arranged for a friend to do this

Why couldn't you get them machined by the seller? Assuming you bought them from China it should be very cheap. It's not easy to do it yourself due to the hardness of the surface.

1) Different tooth shapes which are more/less accurate (backlash etc). HTD is generally considered the best for this application.
2) Could be, but I think they'd be harder to mount and pre-load accurately? Also possibly lower efficiency, but I'm not sure.
3) No since it wouldn't apply an even force on the bearing ring. Belleville washers may not be nessecary - it depends how you mount the bearings. The BK/BF blocks don't use them, instead they rely on the bearings being ground such that when they are tightened together the correct pre-load is applied, or they use shims. If you do use Belleville washers then you can put the ballscrew in tension, which is good since it increases the stiffness of the system a little (or a lot depending).