We’ve all seen it in our personal lives – whether a bolt coming loose on a car, or a piece of furniture or cabinet that has a loose bolt despite you tightening it multiple times. How can you combat this inconvenience? Well, there are actually a large amount of options to choose from, regardless of the application.
By design, standard threads are built to be able to tighten and loosen at will, so a user can assemble and disassemble in any time. However, the exact thing that makes it user-friendly (the ability to loosen bolts) also allows them to unintentionally back off and loosen over time.
How do you combat this? Well, there are a myriad of designs for self-locking fasteners that not only resist loosening – but are left with the ability to break away during intentional loosening.
Chemical Additive Self-Locking Fasteners
The most visible is the application of a small amount of thread-locking adhesive that’s applied directly to the bolt. This adhesive fills the gaps between the male and female fastener, preventing loosening. However, the largest drawback of chemical additive self-locking fasteners is the fact that they’re single-use only.
Essentially, once you tighten a chemical additive fastener, it’ll stay tight. If you loosen it, it’s sayonara to the additive and its gap-filling capabilities.
Thread Deformation / Thread Interruption
Beyond additives, there are other ways to create self-locking components. We can create components that have controlled deformation. That is, the steel of the threads is deliberately chosen to deform when preloaded so it puts the energy into the tightening torque instead of the strain energy of the steel. This tightening torque effectively ‘locks’ and prevents loosening by deforming the thread from its original shape.
Close Tolerance, Extra Grip
Somewhat related to thread deformation / thread interruption, is close tolerances. Instead, the steel of close tolerance threads do not deform upon torqueing the bolt and nut. The third method of achieving maximum torque is to create a closer thread tolerance between the bolt and nut. These closer tolerances resist backing out without the use of adhesive. Plus, because of that lack of adhesive, close tolerance components can be reused – something a chemical additive fastener can never do.
That said, due to the tolerances, there is a limit to the amount of times these fasteners can be used. Over time, if you back out a bolt with a close tolerance, over time, the tolerances are widened due to wear.
Whichever you choose, we can create it for you at Components for Industry. For more information, call one of our Engineers at 847-918-0333.