The Hidden Hero of Fasteners: Friction

Every bolt, nut, and screw you’ve ever used has a secret partner in keeping things together — friction.

When you tighten a bolt or turn a screw, it’s easy to assume that the threads alone are doing all the work. But in truth, it’s the friction between those threads — and between the bolt head or nut and the surface beneath it — that keeps everything from coming loose.

How Friction Holds Things Together

Friction is the invisible force resisting motion between two surfaces. In fasteners, it’s what keeps parts clamped tight even when they’re shaken, heated, or stressed.

When you tighten a bolt, it stretches slightly, creating tension. That tension pushes the threads together, generating friction that resists rotation. The tighter the fit, the more friction — and the more secure the joint.

Without enough friction, bolts could spin free under vibration or pressure. With too much friction, you might not achieve proper clamping force, even if you apply the correct torque.

The Surprising Role of Torque

Here’s a surprising fact: when you use a wrench to tighten a bolt, only about 10% of the torque you apply actually creates the clamping force that holds parts together. The remaining 90% goes into overcoming friction — both in the threads and under the bolt head or nut.

That’s why controlling friction is so important. Lubricants, coatings, and clean surfaces all help maintain consistency, ensuring the right balance between tightness and safety.

Why Friction Prevents Loosening

Once tightened, friction acts like a brake. For a bolt to loosen, it has to overcome both the frictional resistance and the elastic stretch of the bolt itself. That’s not easy — which is why properly tightened fasteners stay secure even under vibration or thermal changes.

For extra protection, engineers often increase friction intentionally with lock washers, nylon inserts, or thread-locking compounds. These additions give the fastener a bit of extra grip — just enough to resist movement without damaging the threads.

In Short

Every fastener you see — from the screws in your chair to the bolts in a skyscraper — relies on friction to do its job. It’s the quiet, unseen force that transforms torque into tension and keeps our world literally held together.

So next time you pick up a wrench, remember: you’re not just tightening metal. You’re harnessing friction — the hidden hero that keeps everything in place.