Zip Fastener Products, Inc engineers have the experience to provide information for you to be able to determine the design of your assembly and fastener. 

If you do not see the information you need, or have questions, please call us at the phone number to the left and we will be glad to help with your design.

We will be adding new information on a regular basis, so check back whenever you need more info. 

This month’s tip is about the nut factor equation.

NUT FACTOR EQUATION

Using this formula you can:

• Predict what assembly torque is needed to achieve a preload target
• Predict what preload is obtained at a chosen assembly torque
• Predict the amount of variation in preload caused by assembly torque tolerancing

T = K x D x F

T = torque (lb-in)

K = nut factor (dimensionless)

D = fastener diameter (in)

F = clamp force (lbs)

K is a measure of friction (not the coefficient of friction) and is available for most coating finishes.  The chart below lists some of the commercially available coatings.

Fastener Finish	Joint Material	Nut Factor
Dry Steel	Dry Steel	.18-.27
Machine Oil	Steel	.10-.26
Cadmium	Steel	.15-.19
Phos & Oil	Steel	.15-.22
Zinc	Steel	.17-.35
302 S.S.	302 S.S.	.30-.50
Dacromet	Steel	.16-.32

 

 If you are interested in learning more about this, please give us a call.