When an axial load is applied, how much axial load is needed to rotate the shaft?
When the friction coefficient between the shaft screw face and the nut screw face is about 0.05 or less, the shaft may rotate under its own weight and the nut may fall off. The normal sliding friction coefficient is said to be 0.1 or more. The friction coefficient, however, may be 0.05 or less depending on the lubricating conditions or the screw surface, and the nut may fall off. Also, it may fall off because of vibration or other factors. The addition of a braking mechanism is recommended.