Abstract: A coupling has an inner member centered on and rotatable about an axis A and formed with a plurality of radially outwardly projecting short inner teeth and a radially outwardly projecting long tooth together defining a plurality of radially outwardly open pockets. The outer end of the long inner tooth defines an orbit centered on the axis and the outer ends of the short inner teeth lie radially inward of this orbit. An outer member coaxially surrounding the inner member is formed with a plurality of radially inwardly projecting short outer teeth and a radially inwardly projecting long outer tooth together defining a plurality of radially inwardly open pockets. The long teeth are angularly juxtaposed with each other and the inwardly open pockets each confront a respective one of the outwardly open pockets.