Abstract: A lock assembly for securing nuts to rotatably driven shafts in which a generally U-shaped locking spring is mounted with one leg thereof disposed along an opening in the rotatably drive shaft or a component keyed to the shaft and the other leg thereof disposed through and beyond a hole in the nut with a tab portion of such leg extending perpendicularly of the hole so that the tab will be urged outwardly of the hole by centrifugal force as the drive shaft is rotated to thereby create a more secure engagement of the locking spring with the nut.