Mechanical Engineering - Machine Design - Discussion

A screw will be self-locking if and only if its efficiency is below 50%.

A screw is said to be self hauling if efficiency is >50%.

I was thinking the same, there is no relation between overhauling and efficiency. Overhauling means screw will automatically lower the load. Technically negative torque required to lower the load ie. Friction angle < lead angle. But it can be also proved by using maths efficiency >50% for overhauling.