One of the major topics we have been discussing is coefficient of friction and the importance of understanding how it can affect your bolted joint. Not all fastener coatings have the same frictional characteristics; some can have a lubricated top coat and some have a non-lubricated top coat (higher friction value). So how does this affect your bolted joint? In most cases if you were to switch to a part that has a lubricated top coat from one without it, you would see bolts stretching and breaking. The cause is that the coefficient of friction has decreased which increased your clamp load at the previous torque value resulting in a failed joint.
The reason it is important to understand this relationship is because it can increase manufacturing costs or even create warranty claims because the changes in friction have a direct relationship to the clamp load created in the joint.
At Bossard we have the capability to perform joint testing so we can help you better understand coefficient of friction and the torque tension relationship in your joints. We can perform testing both onsite at your facility or at one of our engineering design centers. Contact us at ProvenProductivity@bossard.com for more information.