Calculating Addendum and Clearance Coefficients

This may help decipher 3rd party specifications with limited information.

To calculate the coefficients:

·                Click Tools, then select Options.

·                Click on the Company Standards tab.

·                Enter the values for the following:

o                                Pitch diameter

o                                Number of teeth

o                                Addendum length

§                                                Note: Addendum = (major diameter – pitch diameter) / 2

o                                Dedendum length

§                                                Note: Dedendum = (pitch diameter – minor diameter) / 2

o                                Modification, this is sometimes called tool advance. It’s normally negative for the gear and positive for the pinion.