Abstract: A clutch/brake assembly for coupling and decoupling (and simultaneously braking the rotation of) a rotary implement to a drive shaft. The clutch portion of the assembly operates in one mode during low rotational speeds of the implement and at higher rotational speeds changes modes to become a centrifugal clutch. The clutch is also torque sensitive such that when the implement is subjected to high loads and low rotational speeds, the clutch is more tightly engaged to avoid clutch slippage. The brake portion of the assembly has some components common to the clutch assembly. The brake portion is self-energized and constructed to obtain braking assistance from centrifugal force such as at high rotational speeds of the implement and is torque sensitive so that at low rotational speeds and high braking force, the braking surfaces are maintained in tight engagement.