The required lead deviation describes the permissible deviation of the actual lead of a screw drive from the ideal, geometrically intended lead. It is a measure of how accurately the spindle must be manufactured so that the screw drive achieves the required positioning accuracy and repeatability.
What does lead deviation mean?
Every threaded spindle has a nominal lead (e.g., 5 mm/revolution). During production, however, minimal deviations can occur, for example due to grinding precision, thermal distortion, or tool tolerances.
Lead deviation therefore describes:
- how far the real lead deviates from the ideal
- how far the spindle “leads or lags” at a specific point
- how precisely an axis can be positioned
Why do we speak of required lead deviation?
The term describes the maximum deviation permissible in a specific application in order to:
- achieve the specified positioning accuracy
- complete the travel path without errors
- keep backlash and hysteresis low
- ensure a defined repeatability
Manufacturers offer various tolerance classes that allow for different lead accuracies (e.g., C0, C3, C5, C7 for ball screws).
The higher the precision requirements, the smaller the required lead deviation must be selected.