Pitch Line Velocity and what you need to know

Pitch line velocity is the speed that a gear moves at its pitch line, where it comes into contact with another gear and rolls without slipping. The diameter of the pitch line (or pitch circle) is halfway between the root and tip of tooth of the gear.

For module gears: Pitch Diameter = # Teeth * Module

Diametral Pitch gears: Pitch Diameter = # Teeth / DP

The American Gear Manufacturer's Association (AGMA) recommends different grades of oil depending on the pitch line velocity in the gear box, faster velocities need lower viscosities. As modern cutting tools require faster feeds and speeds, we've switched lubricants during some machine upgrades to deliver more speed.

Module DP
Number of Teeth

Gear Pitch (Module/DP)

Rotation Speed (rpm)

Gear Pitch Guide

Recommended oil viscosity based on Pitch Line Velocity, for oils with a Viscosity Index of 90. Check our guide to choosing oils for other Viscosity Indexes.