The load needed to compress or stretch a spring by a unit length, for example N/mm. A spring with a rate of 10 N/mm needs 100 N to compress it by 10 mm (0.394 inch).

Which wire is best for springs?

Music wire and hard drawn wire for general springs, oil-tempered and chrome silicon for higher stress and fatigue, and stainless steel where rust matters.

Why are compression spring ends ground?

Grinding makes the ends flat and square, so the spring stands upright and pushes evenly on the parts at each end.

Spring making job work: types, wire, tolerances

Spring making coils steel or stainless wire into springs on a CNC coiling machine, then stress relieves, grinds and finishes them. The common types are compression springs that push, extension springs that pull, and torsion springs that twist. The wire, coil size, number of turns and free length decide how much load the spring gives at each length.

Quick facts

Main types: Compression, extension, torsion, wire forms
Typical wire: About 0.2–12 mm (0.0079–0.472 inch) on most coilers
Common materials: Music wire, hard drawn wire, oil-tempered wire, SS302/304, chrome silicon
After coiling: Stress relieving; end grinding for compression springs
Load tolerance: Often about ±5–10% unless stated
Usually priced: Per piece, by wire size, turns and quantity

How a spring is made

Wire is fed through a CNC coiler that forms the coils at the set diameter and pitch
Extension spring hooks and torsion spring legs are formed on the coiler or afterwards
Springs are stress relieved in an oven to remove coiling stress and fix the shape
Compression spring ends are ground flat so they stand square
Optional shot peening for fatigue life, then plating, powder coating or oiling
Loads are checked on a spring tester

What changes the spring rate

Change	Effect on stiffness
Thicker wire	Much stiffer (rate rises with wire size to the power 4)
Larger coil diameter	Much softer
More active coils	Softer
Stiffer material	Slightly stiffer (stainless is a little softer than spring steel)

What to send the spring maker

Type of spring and a drawing or sample
Wire size, material and finish
Outside or inside diameter, free length and number of coils
Load needed at one or two working lengths
The hole or rod it must work in or over
Quantity and whether a load test report is needed

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Related job work

Machines

Materials

Questions

What is spring rate?: The load needed to compress or stretch a spring by a unit length, for example N/mm. A spring with a rate of 10 N/mm needs 100 N to compress it by 10 mm (0.394 inch).
Which wire is best for springs?: Music wire and hard drawn wire for general springs, oil-tempered and chrome silicon for higher stress and fatigue, and stainless steel where rust matters.
Why are compression spring ends ground?: Grinding makes the ends flat and square, so the spring stands upright and pushes evenly on the parts at each end.

The figures on this page are typical values for guidance, written by Diemeco from standard engineering practice. They are not a specification: confirm grades and properties with the relevant standard or the supplier's mill test certificate, and tolerances with your workshop. Last checked 22 October 2026.