Single or Double Nut, Preload, Rigidity
This section deals with the various nut types and their preload. We also explain the different rigidity (stiffness) values and why they often cannot be directly compared.
- Single or double nut, lead offset, pitch-shift, ball oversize preload
- How much preload is needed and recommended
Preload primarily serves to eliminate play. But at the same time preload increases rigidity, which means the displacement of the nut under load is reduced.
Another reason why preload may be necessary is to prevent balls from skidding during high acceleration, or to ensure better load distribution if side loads on the ball nut cannot be avoided.
There are a number of ways to preload a ball nut. For a discussion of preload and its effects we have to first distinguish between preload with two contact points per ball (one in the nut, one in the shaft), and preload with 4-point contact (two contact points in the nut and two in the shaft), which requires the use of a "gothic arch" profile.
Steinmeyer always uses a gothic arch profile, so both kinds of preload are possible.