The following timing belt pulley Pitch Diameter (P.D.) and timing belt pulley Outside Diameter (O.D.) charts allow the end user to quickly determine the dimensional requirements for a timing belt drive system. These charts allow the user to check for interferences before a system is designed for a given ratio. This is the second most common problem encountered when talking with an end user. Often the Outside Diameter (O.D.) of a particular timing belt pulley is not considered before a design is finalized.

Timing belt pulley Pitch Diameter (P.D.) has a direct relationship between the timing belt pulley and the timing belt. The reinforcing tensile cord of the timing belt forms the pitch line of the timing belt. Thus the Pitch Diameter (P.D.) of a timing belt pulley coincides with the pitch line of the timing belt meshing with it.

Pitch Diameter (P.D.) = (Pitch x Number of teeth) / Pi (3.14159)

Timing belt pulley Outside Diameter (O.D.) further builds upon the relationship between the timing belt pulley and timing belt. The Outside Diameter (O.D.) of the timing belt pulley is in contact with the tooth bottom of the timing belt while meshing with it. The distance from the timing belt tooth bottom to the tensile cord (pitch line) will determine the Outside Diameter (O.D.) of the timing belt pulley for any timing belt pitch/timing belt tooth profile.

Outside Diameter (O.D.) = Pitch Diameter (P.D.) – (2 x U)
Note: “U” = distance between the tensile cord and the bottom of the timing belt tooth 

 
Rule of Thumb:
To quickly calculate the Outside Diameter (O.D.) in inches of any 8mm pitch timing belt pulley divide the number of teeth on the pulley by ten (10). For example an 80 tooth pulley would have an 8” Outside Diameter (O.D.) (80 teeth / 10) or a 33 tooth pulley would have a 3.3” Outside Diameter (O.D.) (33 teeth / 10).
 

2mm Pitch - Timing Belt Pulley Pitch Diameter and Outside Diameter Charts

2mm PowerGrip GT 2mm STD

3mm Pitch - Timing Belt Pulley Pitch Diameter and Outside Diameter Charts

3mm HTD 3mm PowerGrip GT 3mm RPP 3mm STD

5mm Pitch - Timing Belt Pulley Pitch Diameter and Outside Diameter Charts

5mm HTD 5mm PowerGrip GT 5mm PolyChain GT 5mm RPP 5mm STD

8mm Pitch - Timing Belt Pulley Pitch Diameter and Outside Diameter Charts

8mm CTD 8mm HTD 8mm PowerGrip GT2 8mm PolyChain GT 8mm RPP 8mm STD 8mm YU
  • N/A

9.525mm Pitch - Timing Belt Pulley Pitch Diameter and Outside Diameter Charts

9.525mm HTD2 (RU)
  • N/A

11mm Pitch - Timing Belt Pulley Pitch Diameter and Outside Diameter Charts

11mm HTD
  • N/A
11mm PolyChain GT
  • N/A

14mm Pitch - Timing Belt Pulley Pitch Diameter and Outside Diameter Charts

14mm CTD 14mm HTD 14mm PowerGrip GT2 14mm PolyChain GT 14mm PolyChain HTD 14mm RPP 14mm STD

20mm Pitch - Timing Belt Pulley Pitch Diameter and Outside Diameter Charts

20mm HTD 20mm PowerGrip GT2 20mm RPP

Trapezoidal (Inch) Pitch - Timing Belt Pulley Pitch Diameter and Outside Diameter Charts

2/25" MXL 40 D.P. 1/8" XXL 1/5" XL 3/8" L 1/2" H 7/8" XH 1-1/4" XXH

Trapezoidal (Metric) Pitch - Timing Belt Pulley Pitch Diameter and Outside Diameter Charts

T2.5
  •  
T5
  •  
T10
  •  
T20
  •  

Trapezoidal (Metric) Pitch - Timing Belt Pulley Pitch Diameter and Outside Diameter Charts

AT3 AT5 AT10 AT20
Technical timing belt calculatorcenter to center calculatorpower design
© Pfeifer Industries, LLC. - 2180 Corporate Lane - Suite 104 - Naperville, Illinois 60563-1639 USA
Telephone: (630) 596-9000 Fax: (630) 596-9002