Are Worm Gearboxes Self-Locking?

## The Short Answer Worm gearboxes can be self-locking, but it's not guaranteed. The self-locking ability depends primarily on the **lead angle** of the worm and the **coefficient of friction** between the worm and gear materials. ## When Is a Worm Gearbox Self-Locking? A worm gearbox is considered **statically self-locking** when the worm cannot be driven backwards by the gear. This occurs when: - The lead angle is less than the friction angle - Typically, lead angles below 5° provide reliable self-locking - The gear ratio is high (usually above 30:1) ## Factors That Affect Self-Locking 1. **Lead Angle**: Smaller angles = more self-locking 2. **Material Pair**: Bronze gear + hardened steel worm = better friction 3. **Lubrication**: Less lubrication = more friction = more self-locking (but more wear) 4. **Vibration**: External vibration can break the self-locking condition 5. **Temperature**: Changes material properties and lubrication viscosity ## Important Safety Note **Never rely on worm gearbox self-locking as a safety brake.** Always use a dedicated braking system for lifting applications where failure could cause injury.