How to Calculate a Fastener Clamping Force

Nuts and bolts are basic types of fasteners used to hold things together. The threads of a bolt work like a screw, which is an inclined plane wrapped around a bar. Three types of forces are involved in fastening something together with bolts and nuts. First is the preload force, which is the amount of force that is exerted to turn the nut or bolt. This value is determined from the torque. The second force is the tension force, which is the force the materials held together exert on the nut and bolt. The difference between these forces results in the clamping force, which is the force holding everything together.

Things You'll Need

• Nut
• Bolt
• Material to fasten together
• Force transducer

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Instructions

1. • 1

     Determine the preload force. Measure it with a force transducer while turning the nut or bolt.

   • 2

     Determine the tension force. Measure this with the force transducer as well.

   • 3

     Subtract the tension force from the preload force using the equation:

     F(clamping) = F(preload) - F(tension). The result is the clamping force the nut and bolt use to hold material together.

   • 4

     If multiple nuts and bolts are used to hold material together, add the clamping force for each one to find the total clamping force.