Roller chain couplings have a torque capacity in excess of the torque normally transmitted by shafting which falls within the coupling bore range. Select the smallest coupling, which will accommodate both shafts. For a reversing operation, shock or pulsating loads, or other severe operating conditions. select the next larger coupling size. A cover should be used to assure Max service life, particularly if the coupling operates at high speeds or under moist conditions. For proper lubrication, fill the space between the cover and the coupling with soft to medium consistency coupling grease. Many finished bore size. available as well as stock bore blanks that Can be altered. Chains, covers stocked in all branch locations. All stock roller chain couplings have hardened teeth. Martin Roller Chain Sprocket Coupling Hub, Bored-to-Size, Chain Number: 50, 7/8 in Bore Dia, 18 Teeth, 3.72 in Outside Dia, 2.969 in Hub Dia, 3/16 x 3/32 in Keyway, 3600 RPM Maximum, 1-11/16 in Hub Length, 1.688 in Length Through Bore, 1/4-20 x 1/4 in Screw, Steel