Clutch

A reliable mechanical clutch is disclosed. The clutch includes a clutch assembly and an engagement assembly together selectively coupling or decoupling driving and driven members. The gist of the present invention lies in grooves of end-to-end gradually reduced depth are formed on interfacing faces between active and passive rings where balls are accommodated to roll. The active and passive rings, when turned, would be close to or away from each other, thereby causing the clutch assembly to function. The clutch is therefore structurally simple, has a low failure rate, and may effectively reduce its form factor and production cost. Its function is purely through mechanical operation with limited triggering force but produce a powerful push, thereby achieving greater reliability.