Abstract: A brake (10) for applying a braking force to a shaft includes a housing (11) which defines a chamber (17). The housing (11) includes a plurality of depressions (19) which are circumferentially spaced around an axis (22). A rotatable actuator (40) is received in the chamber (17) and includes a plurality of depressions (43) circumferentially spaced around the axis (22). The housing depressions (19) face the rotatable actuator depressions (43) and each matching pair of depressions receive a ball (23) therebetween. A spring (50) under compression is positioned centrally about the axis (22). A bearing (56) is interposed between the rotatable actuator (40) and disc assembly (70). When the rotatable actuator (40) is rotated, the balls (23) roll along the depressions (19, 43) to gradually shallower portions thereof. This in turn moves the rotatable actuator (40) axially away from the housing (11), thereby applying a braking force to the shaft.