Set screw D-hubs are a fantastic solution for transferring power from a shaft to the hub. While conventional hubs with a cylindrical bore rely solely on the set screw to keep the hub from slipping on the shaft, the new D-hubs have a D-shaped bore to perfectly match a D-shaft of the same diameter. This means that, even without a set-screw, the hub is prevented from slipping on the shaft. The 10-32 set-screw, when tightened, will apply pressure to the flat of the D-shaft for added security and to keep the D-hub from sliding up and down the shaft. Since the set screw contacts the flat of the shaft it makes removal of the hub very easy - no marring of the cylindrical surface which would interfere with the installation/removal of parts such as ball bearings. The hubs are fully machined from 6061 T6 aluminum so that we can hold tight tolerances and ensure they fit perfectly with mating parts. The 0.770" Actobotics® pattern is tapped into the face of the part so that you can install gears, wheels, pulleys, sprockets, etc. with 6-32 machine screws.