Key Force Calculator, Formula, KF Calculation

Key Force Calculator

Enter the values of torque, T(lbf-in) and diameter of the shaft, D(in) to determine the value of key Force, KF(lbf).

Enter Torque: lbf-in
Enter Diameter: in
   
Result – Key Force: lbf

Key Force Formula

The key force in mechanical contexts often refers to the force exerted by or on a key that is used in a mechanical assembly to transmit torque from a shaft to an attached component, like a gear or pulley.

Key Force, KF(lbf) in pounds-force is calculated by doubling the torque, T(lbf-in) in pounds-force inches and dividing by the diameter of the shaft,D(in) in inches.

Key Force, KF(lbf) = 2 * T(lbf-in) / D(in)

KF(lbf) = key force in pounds-force, lbf.

T(lbf-in) = torque in pounds-force inches, lbf-in.

D(in)  = diameter in inches, in.

Key Force Calculation:

  1. Calculate the Key Force required for a torque of 100 lbf-in applied on a shaft with a diameter of 2 inches.

Given: T(lbf-in) = 100lbf-in, D(in)  = 2in.

Learn More:   kVAR to Farad Conversion Calculator (μF, mF, F)

Key Force, KF(lbf) = 2 * T(lbf-in) / D(in)

KF(lbf) = 2 * 100 / 2

KF(lbf) = 100lbf.

  1. Assume you need to find the diameter of a shaft that is subjected to a torque of 120 lbf-in, and the required key force is 240 lbf.

Given: T(lbf-in) = 120lbf-in, KF(lbf) = 240lbf.

Key Force, KF(lbf) = 2 * T(lbf-in) / D(in)

D(in)  = 2 * T(lbf-in) / KF(lbf)

D(in)  = 2 * 120 / 240

D(in)  = 1in.

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