For Square Nut — GB/T 39 / ISO 4034 (Series 075), T 39 defines dimensions, tolerances and product grades. The sections below describe its scope, what it does NOT cover, and the equivalents across DIN, ISO and ASME.
T 39 — Scope
T 39 specifies the dimensions and tolerances of square nut — gb/t 39 / iso 4034 (series 075). 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
T 39, alongside the related GB/T 39 / ISO 4034 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 T 39
| Size | Pitch (mm) | Width across flats s (mm) | Nut height m (mm) | Reference standard |
|---|---|---|---|---|
| M3 | 0.5 | 5.5 | 1.8 | GB/T 39 / DIN 562 |
| M4 | 0.7 | 7.0 | 2.2 | GB/T 39 / DIN 562 |
| M5 | 0.8 | 8.0 | 2.7 | GB/T 39 / DIN 562 |
| M6 | 1.0 | 10.0 | 3.6 | GB/T 39 / DIN 562 |
| M8 | 1.25 | 13.0 | 4.8 | GB/T 39 / DIN 562 |
| M10 | 1.5 | 17.0 | 6.0 | GB/T 39 / DIN 562 |
| M12 | 1.75 | 19.0 | 7.0 | GB/T 39 / DIN 562 |
| M16 | 2.0 | 24.0 | 9.0 | GB/T 39 / DIN 562 |
| M20 | 2.5 | 30.0 | 12.0 | GB/T 39 / DIN 562 |
| M24 | 3.0 | 36.0 | 14.0 | GB/T 39 / DIN 562 |
Equivalent Standards
Where direct equivalents exist (ISO ↔ DIN, ISO ↔ ASME), they are listed on the parent Square Nut — GB/T 39 / ISO 4034 (Series 075) page. Always confirm against the dimensions on this page, since some "equivalent" standards differ in tolerances and head geometry.
When to Specify T 39
Choose T 39 for international engineering work and OEM supply where ISO standards are the contractual reference. It is the default modern specification for square nut — gb/t 39 / iso 4034 (series 075).