Word of the Day 12 September 2026

case hardening

The process of imparting greater hardness to the surface of a piece of metal.

Why this one

A hard surface over a tough core, so the part resists wear without becoming brittle the whole way through.

In use

Don't grind past the case hardening on those gear teeth or you're straight into soft metal and it'll wear out in a month.

Written by our editors to show how the term is used, not a recorded quotation.

Sources