Screw Jacks with 24:1 and 25:1 gear ratios are considered self-locking in most cases.

The following screw jack models are considered not to be self-locking:

• All Metric and Imperial ball screw jacks
• The M2555 (1/4 ton) screw jacks with 5:1 gear ratio
• The E2625 (5kN) & M2625 (1/2 ton) screw jacks with 5:1 gear ratio
• The E2501 (5kN) & M2501 (1-ton) screw jacks with 5:1 gear ratio
• In some cases the E1802 (25kN), M1802 & M9002 (2 ton) screw jacks with 6:1 gear ratio. For advice on an application basis consult Power Jacks Ltd
• In some cases the E1805 (50kN) & M1805 (5 ton) screw jacks with 6:1 gear ratio. For advice on an application basis consult Power Jacks Ltd
• In some cases the E1810 (100kN) & M1810 (10 ton) screw jacks with 8:1 gear ratio. For advice on an application basis consult Power Jacks Ltd
• In some cases the M1815 (15 ton) screw jacks with 8:1 gear ratio. For advice on an application basis consult Power Jacks Ltd

All screw jacks with double start lifting screws are considered not to be self-locking. Screw Jacks considered not self-locking will require a brake or other holding device (refer to E-Series Screw Jacks brochure (P69)). If vibration conditions exist, refer to E-Series Screw Jacks brochure (P86). However for detailed advice and analysis consult Power Jacks Ltd