One of the most important branches of re-manufacture is that of tool making. Nearly all tools are made of steel. Those used for measuring and trying, such as calipers, gages, squares and scales, are sufficiently hard and durable when made of low-carbon steel.

Tools for metal cutting are forged from high-carbon or alloy-crucible steels of the best quality. Carbon steel for tools is commonly known as machinery steel.

A lasting keen edge on a cutting tool requires hardness, but hardness and brittleness go together, hence those tools which must stand extreme shocks, battering, twisting, or bending, must sacrifice some of the hardness to tenacity and ductility.

Cutting tools may be forged or cast to approximate shape. The rougher tools may be hardened and then ground to finished shape, but the tools for finer work, as taps and dies, must be machined to shape before they are hardened. The process of hardening may distort a tool slightly, which may ruin it unless it can be brought to its true shape by grinding after hardening.