Well here goes... Aluminium frame router design

[Lee Roberts]

Is that how the preload is set then? with slightly larger ball's?

Hiya,

Pretty much yes, if you use slightly bigger ball bearings than the distance between the carriages and rail.

The ball bearing size (relative) determines the amount of preload achieved. From what I've read, the most common amounts of preload used for linear guides are 8, 5 and 2 percent of their load rating (dynamic).

For ballscrews and nuts you can do the same thing with the ball sizing, use an adjustable nut or use two nuts.

.Me