Coiled Compression Springs from Music Wire

Coil springs are wound from wire. In a coiling machine, rollers pull straight spring wire into guides that bend it into a helix; the tooling sets the spring's shape. Coiling leaves stresses in the wire, so the springs are then stress relieved at a raised temperature. The ends of compression springs are often ground flat, around 270° of the end coil, so the spring stands square.