Abstract: A simple, adjustable shaft coupling employed for accurately advancing or retarding the timing of shafts, sprockets, cams, gears, levers and the like made up of a pair of annular disks, each fixed to a hub member by injection molding or a similar process to effect integration of parts, each disk having a plurality of openings therethrough with the number of openings in the two disks differing. Alignment of matching sets of openings in the two disks provides desired rotational adjustment therebetween. In the particular model described a total of 544 locking positions, producing adjustment accuracy in the order of 1/6 or 1.degree., is available. The hub members are interferingly anchored to the disks and are capable of attachment to input or output shafts and provide for optional face mounting thereto of gears, sprockets, cams and the like.