T 5281 is the international standard for socket head shoulder screw — gb/t 5281 / iso 7379 (series 017). This page sets out what the standard governs, the size range it specifies, and the related standards you will see referenced in datasheets.
T 5281 — Scope
T 5281 specifies the dimensions and tolerances of socket head shoulder screw — gb/t 5281 / iso 7379 (series 017). 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 5281, alongside the related GB/T 5281 / ISO 7379 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 5281
| Shoulder dia (mm) | Thread size | Pitch (mm) | Shoulder length (mm) | Head dia dk (mm) | Head height k (mm) | Reference standard |
|---|---|---|---|---|---|---|
| 5 | M4 | 0.7 | 16 | 9.5 | 5.3 | ISO 7379 / GB/T 5281 |
| 6 | M5 | 0.8 | 20 | 11.0 | 6.5 | ISO 7379 / GB/T 5281 |
| 8 | M6 | 1.0 | 25 | 13.0 | 8.0 | ISO 7379 / GB/T 5281 |
| 10 | M8 | 1.25 | 30 | 16.0 | 10.0 | ISO 7379 / GB/T 5281 |
| 12 | M10 | 1.5 | 40 | 18.0 | 12.0 | ISO 7379 / GB/T 5281 |
| 16 | M12 | 1.75 | 50 | 24.0 | 16.0 | ISO 7379 / GB/T 5281 |
| 20 | M16 | 2.0 | 60 | 30.0 | 20.0 | ISO 7379 / GB/T 5281 |
| 25 | M20 | 2.5 | 80 | 36.0 | 25.0 | ISO 7379 / GB/T 5281 |
Companion Standards
T 5281 controls only the geometry of socket head shoulder screw — gb/t 5281 / iso 7379 (series 017). 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).
When to Specify T 5281
Choose T 5281 for international engineering work and OEM supply where ISO standards are the contractual reference. It is the default modern specification for socket head shoulder screw — gb/t 5281 / iso 7379 (series 017).