How Bolts Become Loose and Ways to Prevent Them?

A loose bolt on heavy duty equipment may not seem like a big issue at first thought, but the reality is that the tiniest bolt can cause the biggest issues, if not properly installed. A loose bolt on a helicopter, for instance, can potentially cause a whole series of issues down the road. That’s why it’s important to keep an eye on the bolts in your aircraft and be proactive in implementing measures to prevent them from becoming loose. Below you’ll see a few different reasons why a bolt may become loose and some things that you can do to prevent that.

Causes of Loose Bolts

Shock: Long hours with alternating heavy loads can create a lot of strain on machinery, no matter how fortified or robust it may have been built. While the bolts may be able to withstand impact and heavy loads, the more frequent it has to endure it, the worse the wear. A sudden force applied to the bolt or the joint can cause the bolt to slip relative to the threads of the joint, the slippage of which can ultimately lead to bolts loosening.

Under-tightening: As is evident on any kind of assembled machinery, a loose bolt that is not properly tightened cannot be guaranteed to hold upright any adjoining segments together. By definition, the joint does not have enough clamp force to hold the individual sections together. This could potentially lead to sideways slippage between adjoining parts, which places an unbearable stress on the bolt that could eventually cause the entire assembly to break.

How To Prevent

Washers: There are many types of washers that have been designed with ribs, fluting, or teeth that cling to the surface of the joint while it is being tightened. The only con for this method is that it can result in permanent damage to the joint finish or surface, which may ultimately deem it as unacceptable according to FAA AC 0056B and other aviation regulations.

Mechanical devices: There are a number of ways that you can prevent a too-loose bolt and one of them is simply by using mechanical devices to lock a tightened nut into place on a bolted joint. Castellated nuts, for example, have a slotted end and are used with a cotter pin or wire that fits through a hole drilled in the bolt. On the other hand, tab washers have two tabs on opposite sides, which fold up to secure the bolt head or nut after installation, and may have teeth that can penetrate the surface of the joint to hold it in place.

Ultimately, there are several methods that you can implement to ensure your bolts are properly installed and maintained. For more information on bolts or other fasteners, reach out to the expert team at ASAP Fasteners.


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