What is lock wire?

Lock wire or safety wire is applied in situations where extreme mechanical reliability is needed. Aircraft use a lot of lockwire to secure fastners. So do aerospace companies and a lot of car and bike racers. Here's how it works.

Imagine a bolt and nut. Now imagine the bolt having a hole drilled through it near the end of the threads away from the head. Put the bolt in the bolt hole using washers if needed and fit the nut. Tighten it up. Now do the rest of the bolts and nuts that hold this cover in place. You now have all these bolts with a little bit of their threads sticking through the nuts, and the hole we talked about is visible. Take a long piece of flexible wire - lock wire - and put it through one hole. Then twist it to the point where it reaches another bolt and put the wire through the the hole in that bolt. Repeat until all the fasteners are lock wired. Even if a nut or multiple nuts come loose, they can't get off the bolts because of the lockwire. Sometimes bolt heads are drilled for lock wire and it's put through the heads of the fasteners, twisted and then secured.

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