Specification summary of T 818 as applied to phillips pan head machine screw: the dimensions the standard controls, the tolerance and product grades it defines, the full specified size range, and the equivalent DIN/ISO/ASME designations.
T 818 — Scope
T 818 specifies the dimensions and tolerances of phillips pan head machine screw — gb/t 818 / iso 7045 (series 034). 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 818, alongside the related GB/T 818 / ISO 7045 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 818
| Size | Pitch (mm) | Length L (mm) | Head diameter dk (mm) | Head height k (mm) | Cross recess | Reference standard |
|---|---|---|---|---|---|---|
| M3 | 0.5 | 20 | 5.6 | 1.8 | PH1 | ISO 7045 / GB/T 818 |
| M4 | 0.7 | 25 | 8.0 | 2.4 | PH2 | ISO 7045 / GB/T 818 |
| M5 | 0.8 | 30 | 9.5 | 3.0 | PH2 | ISO 7045 / GB/T 818 |
| M6 | 1.0 | 40 | 12.0 | 3.6 | PH3 | ISO 7045 / GB/T 818 |
| M8 | 1.25 | 50 | 16.0 | 4.8 | PH3 | ISO 7045 / GB/T 818 |
| M10 | 1.5 | 60 | 20.0 | 6.0 | PH4 | ISO 7045 / GB/T 818 |
Companion Standards
T 818 controls only the geometry of phillips pan head machine screw — gb/t 818 / iso 7045 (series 034). 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 818
Choose T 818 for international engineering work and OEM supply where ISO standards are the contractual reference. It is the default modern specification for phillips pan head machine screw — gb/t 818 / iso 7045 (series 034).