Variation in the spacing of teeth around the gear. Single pitch deviation compares each tooth's position with the ideal one pitch from its neighbor, while cumulative pitch deviation sums the errors around the whole gear and shows eccentricity or indexing problems. Spacing errors produce once-per-revolution and tooth-to-tooth variation in motion, adding noise and dynamic load.
Cumulative pitch deviation is a sine wave around the gear, it's eccentric, the bore was ground off center.
Also heard as
- index error
- spacing error
- cumulative pitch error
Related terms
Runout
How much the teeth wobble radially relative to the gear's axis, measured with a probe in each tooth space.
Circular pitch
The arc distance from one tooth to the same point on the next tooth, measured along the pitch circle.
Ghost frequency
A gear noise tone that matches no tooth count in the box, left behind by errors in the cutting machine.
AGMA quality number
A grade that sets how accurate a gear's teeth must be, on either the Q-number or the A-number scale.