Standard machine screw jacks, machine screw jacks with anti-backlash and ball screw jacks must be considered separately, as the normal backlash will vary due to different constructions.

Backlash in Standard Machine Screw Jacks Machine screw jacks have backlash due not only to normal manufacturing tolerances, but to the fact that there must be some clearances to prevent binding and galling when the screw jack unit is under load (for values refer to E-Series Screw Jacks brochure (P25)). Usually, the backlash is not a problem unless the load on the screw jack unit changes between compression and tension. If a problem does exist, then a unit with the anti-backlash feature should be considered.

Screw Jacks with the Anti-Backlash Device The anti-backlash device reduces the axial backlash in the lifting screw and nut assembly to a regulated minimum. As the backlash will increase as the lifting screw thread on the gear wears the anti-backlash device can be adjusted to remove this normal condition.

Ball Screw Jacks Ball screw jacks do not have an anti-backlash option similar to the machine screw jacks. Instead for zero or reduced axial play ball screw jacks can be ordered with a pre-loaded ball nut (refer to E-Series Screw Jacks brochure (P45)).