Number of Teeth (Chordal Action)Nom. Pitch DiameterNom. Outer Diameter Nom. Hub Width Available Bore Sizes
inmminmminmmRound in1Square inRound mm1Square mm
12 (3.41%)2.3582.4611.0251-7/16
12 (3.41%)2.6662.7701.0251-7/16
12 (3.41%)3.0763.1781.0251-7/16
12 (3.41%)3.3843.4871.0251-7/16
12 (3.41%)3.7943.8961.0251-7/16
12 (3.41%)4.01024.11041.0251-7/16
12 (3.41%)4.41124.51131.0251-7/16
12 (3.41%)4.71194.81221.0251-7/16
12 (3.41%)5.11305.11311.0251-7/16
12 (3.41%)5.41375.51391.0251-7/16
12 (3.41%)5.81475.81481.0251-7/16
12 (3.41%)6.21576.21571.0251-7/16
12 (3.41%)6.51656.51651.0251-7/16
12 (3.41%)6.91756.91741.0251-7/16
  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.