Number of Teeth (Chordal Action)Nom. Pitch DiameterNom. Outer DiameterNom. Hub WidthAvailable Bore Sizes
inmminmminmmRound in1Square inRound mm1Square mm
15 (2.19%)5.11305.31351.5381, 1-3/161.530, 4040
17 (1.70%)5.81476.11551.538 30, 4040
18 (1.52%)6.11556.31601.5381-1/4, 1-1/21.5, 2.5 40, 60
20 (1.23%)6.81737.01781.5381-1/41.5, 2.5 40, 60
  1. Round bore molded and split sprockets are frequently furnished with two keyways. Use of two keys is NOT REQUIRED nor recommended. Round bore sprockets do not have setscrews for locking the sprockets in place. As with square bore sprockets, only the center-most sprocket must be locked down. 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.