A spring is a machine that stores energy in torsion while pretending to work in compression. Push down on a helical coil and the wire itself never really compresses — it twists. Every unit of load becomes shear stress running along the wire’s length. Getting that geometry right is what spring making is really about. It starts with the wire. High-carbon or alloy steel — music wire, oil-tempered, chrome-silicon — is patented (austenitised, then cooled through a lead or salt bath to fine pearlite) and cold-drawn through progressively smaller dies. Work hardening pushes tensile strength past 2000 MPa in the thinnest gauges. Coiling then forms the helix: - Cold coiling: wire is driven through feed rollers against fixed coiling points that curl it to diameter, while a pitch tool nudges each new loop sideways - Hot coiling: heavy wire is heated to austenitising temperature, wound on a mandrel, then quenched and tempered — used where cold work would crack the section Pitch, the axial gap b...