Classical V-belt Sheave Diameters

Three different sheave diameters are used for classical-section V-belts, depending on what information is needed. The table below summarizes the most common uses:

The table below can be used to determine pitch and datum diameters based on the sheave outside diameter.  To calculate pitch or datum diameter, subtract the indicated value in the table from the sheave outside diameter.

Note:  all values are in inches.

Calculating Pitch Diameter for Synchronous Sprockets / Pulleys

If you know the number of sprocket grooves and the belt pitch (distance from the center of one belt tooth to the center of the next), you can easily calculate sprocket (or pulley) pitch diameter:

     Metric Pitch Belts / Sprockets:
     sprocket pitch diameter (in) = 0.012532 × pitch (mm) × # grooves

     Timing Belts / Pulleys:
     pulley pitch diameter (in) = 0.31831 × pitch (in) × # grooves

Pitch and number of grooves can typically be identified using the part number:

     Metric Pitch Example - 14MX-40S-68:
     sprocket pitch diameter (in) = 0.012532 × 14 mm × 40 grooves = 7.018 in

    Timing Example - TL40H150:
     pulley pitch diameter (in) = 0.31831 × 0.50 in × 40 grooves = 6.366 in