Welcome back to the world of fastening technology. Today, we’re taking a closer look at how hard fasteners really are—and why this plays a key role in components such as set screws, cylindrical pins, and washers.

What Is a Hardness Test?

Hardness testing determines how strongly a material resists localized deformation. A defined force is applied to a very small area, and the resulting deformation is then evaluated to determine how much the material yields.

How Is Hardness Tested?

Methods range from simple comparative tests to highly precise laboratory testing. In industrial practice, microscopic hardness testing methods are used in particular.

We use a measuring microscope with a diamond indenter to determine Vickers hardness. A pyramid-shaped diamond is pressed into the surface with a precisely defined test force. The resulting indentation is measured under a microscope and converted into a reproducible hardness value.

This method is particularly suitable for:

–Small components such as set screws or cylindrical pins

–Thin surface layers and hardened surfaces

–Localized testing without requiring large amounts of material

Why Is Hardness Testing So Important?

Hardness provides important information about the serviceability and service life of a fastener:

–Too soft: Increased risk of wear, plastic deformation, or loss of function

–Too hard: Risk of brittle fracture under dynamic or impact loads

Especially for precision fasteners such as washers, locating pins, or set screws, the right hardness is essential for proper fit, load transfer, and safety.

The Screw Icon’s Words of Wisdom:

It’s not just the hardness value that matters, but also the location of the measurement. Whether at the surface, in the core, along the component, or across it, each measurement location provides important information.
The Vickers method makes it possible to precisely identify these differences while minimizing material damage.

Conclusion

Hardness is not a matter of feel, but a measurable material property.
And for fasteners such as set screws, cylindrical pins, and washers, it is a key factor in their function, safety, and reliability.