Shaft collars hold bearings and sprockets to shafts and other components and can act as mechanical stops. One-piece shaft collars slide onto the end of a shaft and lock in place. Two piece collars separate in the center to be installed around equipment while still in service. Set screw collars are held in place with a threaded grub or hex set screw. Thin shaft collars are lightweight and smaller in dimension for high speed, low clearance applications. Double wide collars feature extended length. Heavy duty collars are thicker material for increased grip on large shafts in demanding lateral load scenarios. Mountable shaft collars have an internally threaded portion to rigidly mount and positively locate shaft or component. Mountable clamping lever shaft collars have the same mounting holes as other mountable shaft collars with the addition of a clamping lever for fast adjustments. Clamping lever and cam lever quick-clamping collars are installed and repositioned tool-free. Shaft collars for threaded shafts, keyed shafts, D-shafts, and hexagonal shafts positively interact the inside profile of the collar to the exterior profile shaft of the corresponding shafts, ensuring rotational stability. Bearing locknuts thread into place to positively locate and seat a bearing in position.