Abstract: A harvester reel adjusting and locking mechanisms for positioning the bearing carrier at each end of the reel axle at a selected distance along the support arm on which it is slidable. The carrier is provided with holes which are capable of registering with a series of closely spaced holes in the outer end region of the support arm. An operating tool having a vertical shank portion serves to lock the carrier in an adjusted position when such shank is projected through one of the holes in the carrier and a selected registering hole in the support arm. A radial displacement cam is disposed on the shank portion and is of such extent that when the shank portion is positioned in a hole immediately forwardly or rearwardly of the carrier and then rotated through an angle of 180.degree.