Enter the torque applied to the bolt, the diameter of the bolt, and the coefficient of friction for the bolt contact to determine the clamping force.

## Clamping Force Formula

The following formula is used to calculate the axial clamping force of a bolt.

F = T / K * D

• Where F is the clamping force (N, lbs)
• T is the torque applied to the bolt (N-mm, in-lb)
• K is the friction of the bolt contact
• Steel = .2
• Lubricated = .17
• D is the diameter of the bolt ( mm, in )

## Clamping Force Definition

What is a clamping force? A clamping force is a measure of the force applied to an object that is used to oppose separating forces that are trying to move that object from its current location.

## Example Problem

How to calculate clamping force?

1. First, determine the torque applied to the bolt.

Using a torque wrench, the torque being applied to the bolt in this example is found to be 300 in-lbs.

2. Next, determine the diameter of the bolt.

The bolt being used in this application is a measure to be 2 inches.

3. Next, determine the friction of the bolt.

In this example, the bolt is a standard steel bolt. The friction is assumed to be .2. In reality, this could vary slightly depending on several factors, but .2 is a good estimate.

4. Finally, calculate the clamping force.

Using the formula, the clamping force is found to be 300/(2*.2) = 750 lbs of force.