Enter the total torque transmitted by the shaft and the diameter of the shaft into the calculator to determine the key force.

Key Force Formula

The following equation is used to calculate the Key Force.

KF = T*2/D

  • Where KF is the key force (lbf)
  • T is the torque applied to the key (lbf-in)
  • D is the diameter of the shaft (in)

What is a Key Force?

Definition:

A key force is the total force, including direct and shear force, acting on a key during operation.

How to Calculate Key Force?

Example Problem:

The following example outlines the steps and information needed to calculate the Key Force.

First, determine the torque applied to the key . In this example, the torque applied to the key is found to be 50 lbf-in.

Next, determine the shaft diameter. For this problem, the shaft diameter is found to be 4 in..

Finally, calculate the Key Force using the formula above:

KF = T*2/D

KF = 50*2/4

KF = 25 lbf