COLD-WORK
Cold-working is a technique which, by smoothing, allows the material to harden on the surface while keeping its core soft. This technique has the advantage of hardening a component on the surface without making it more breakable.
This technique is used on pivots, whether cylindrical or conical. Also cold-work is sometimes used in the process of polishing the angle of bridges or other parts. The tool used for cold-working is often the burnisher.