Extension Spring manufactured to ISO are dimensioned by the size table reproduced on this page. The standard fixes geometry and tolerances only; material and property class are assigned by ISO 898-1/898-2, and surface finish by separate finish standards.
ISO — Scope
ISO specifies the dimensions and tolerances of extension spring — iso / din (series 143). Material, property class, surface finish and packaging are governed by separate documents in the same standards family (for example ISO 898-1 for the mechanical property classes of bolts and screws).
Tolerance & Product Grades
ISO, alongside the related ISO / DIN entries on this site, specifies product grades (typically A or B for fine work and C for general engineering) and tolerance classes for the controlling dimensions. Choose the grade against the precision your application requires.
Dimensions Specified by ISO
| Wire dia d (mm) | Outer diameter De (mm) | Free length Lo (mm) | Initial tension F0 (N) | Rate k (N/mm) | Material | Reference standard |
|---|---|---|---|---|---|---|
| 0.8 | 6 | 30 | 2 | 2.5 | Music wire | DIN 2097 / GB/T 23935 |
| 1.0 | 8 | 40 | 4 | 4.0 | Music wire | DIN 2097 / GB/T 23935 |
| 1.2 | 10 | 50 | 6 | 6.5 | Music wire | DIN 2097 / GB/T 23935 |
| 1.6 | 14 | 70 | 10 | 12.0 | Music wire | DIN 2097 / GB/T 23935 |
| 2.0 | 18 | 90 | 18 | 20.0 | Music wire | DIN 2097 / GB/T 23935 |
| 2.5 | 22 | 120 | 28 | 32.0 | Music wire | DIN 2097 / GB/T 23935 |
| 3.0 | 28 | 150 | 45 | 55.0 | Music wire | DIN 2097 / GB/T 23935 |
| 4.0 | 40 | 200 | 90 | 110.0 | Music wire | DIN 2097 / GB/T 23935 |
Equivalent Standards
Where direct equivalents exist (ISO ↔ DIN, ISO ↔ ASME), they are listed on the parent Extension Spring — ISO / DIN (Series 143) page. Always confirm against the dimensions on this page, since some "equivalent" standards differ in tolerances and head geometry.
Companion Standards
ISO controls only the geometry of extension spring — iso / din (series 143). The mechanical strength is set by ISO 898-1 (bolts and screws) or ISO 898-2 (nuts); the surface finish is governed by separate finish standards (e.g. ISO 4042 for electroplating). For corrosion testing, the relevant document is ISO 9227 (neutral salt spray).