Ball Spline Assy, with pulleys (02574-000F)

A ball spline is a type of rolling bearing linear guide, similar to a round shaft and bushing assembly, but with a critical distinction in its operation. The shaft of a ball spline is much like a linear guide shaft, except that the spline shaft has grooves along its length. The spline nut (analogous to the bearing, or bushing, of a traditional rolling bearing guide) contains circuits of recirculating balls. But instead of the spline nut riding freely on the shaft with the ability to rotate as it travels, the load-carrying balls ride in the shaft grooves, which constrains the spline nut from rotating.