Abstract: A self-contained mechanical actuator, such as a jackscrew, which includes a housing in which a drive shaft assembly connects a power source to the input side of a speed reduction gear train, the output of which is associated with load-bearing means for manipulation of a load. A brake is provided in association with the drive shaft assembly where a minimum braking force can be used to maximum advantage. The brake includes a carrier member mounted about the drive shaft assembly solely by a plurality of ball elements carried by the carrier member and biased against the drive shaft assembly to apply a braking force against the shaft.