Number of Teeth (Chordal Action)Nom. Pitch DiameterNom. Outer Diameter Nom. Hub Width Available Bore Sizes
inmminmminmmRound in1Square inRound mm1Square mm
12 (3.41%)3.9993.9990.75191.251.5 40
16 (1.92%)5.11305.21321.5381.25, 1.51.53040
18 (1.52%)5.71455.81481.5381.251.525, 30, 4040
  1. U.S. key sizes on round bore sprockets are based on ANSI standard B17.1-1967 (R1989) and metric key sizes are based on DIN standard 6885.