T 845 covers the dimensional requirements for sheet-metal self-tapping screw. Reproduced below: the complete size table, the tolerance grades, and the companion and equivalent standards referenced when ordering to this document.
T 845 — Scope
T 845 specifies the dimensions and tolerances of sheet-metal self-tapping screw — gb/t 845 / iso 7049 (series 045). 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 845, alongside the related GB/T 845 / ISO 7049 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 845
| Size | Nominal diameter (mm) | Pitch (mm) | Length L (mm) | Head diameter dk (mm) | Head height k (mm) | Reference standard |
|---|---|---|---|---|---|---|
| ST2.2 | 2.2 | 0.8 | 9.5 | 4.2 | 1.4 | ISO 1481 / GB/T 845 |
| ST2.9 | 2.9 | 1.1 | 13 | 5.6 | 1.7 | ISO 1481 / GB/T 845 |
| ST3.5 | 3.5 | 1.3 | 16 | 6.9 | 2.1 | ISO 1481 / GB/T 845 |
| ST3.9 | 3.9 | 1.3 | 16 | 7.5 | 2.3 | ISO 1481 / GB/T 845 |
| ST4.2 | 4.2 | 1.4 | 19 | 8.2 | 2.5 | ISO 1481 / GB/T 845 |
| ST4.8 | 4.8 | 1.6 | 25 | 9.5 | 2.9 | ISO 1481 / GB/T 845 |
| ST5.5 | 5.5 | 1.8 | 32 | 10.9 | 3.3 | ISO 1481 / GB/T 845 |
| ST6.3 | 6.3 | 1.8 | 38 | 12.5 | 3.8 | ISO 1481 / GB/T 845 |
Companion Standards
T 845 controls only the geometry of sheet-metal self-tapping screw — gb/t 845 / iso 7049 (series 045). 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 845
Choose T 845 for international engineering work and OEM supply where ISO standards are the contractual reference. It is the default modern specification for sheet-metal self-tapping screw — gb/t 845 / iso 7049 (series 045).