Grade 12.9 Steel Hex Socket Flat Point Set Screw — GB/T 77 / ISO 4026 (Series 021) pairs the standard GB/T 77 / ISO 4026 with a Grade 12.9 Steel base material. The sections below cover why engineers select this grade for hex socket flat point set screw — gb/t 77 / iso 4026 (series 021), its corrosion and temperature behavior, and the sizes available.
Why Choose Grade 12.9 Steel for Hex Socket Flat Point Set Screw — GB/T 77 / ISO 4026 (Series 021)
The highest common strength class, for high-load machine assembly. For hex socket flat point set screw — gb/t 77 / iso 4026 (series 021), this matters when requires plating or black-oxide protection is the primary requirement.
Mechanical & Physical Properties
| Grade designation | class 12.9 |
|---|---|
| Magnetic response | Magnetic |
| Service temperature | up to approx. +300 °C |
| Corrosion characteristic | Requires plating or black-oxide protection |
Corrosion Behavior in Service
Carbon and alloy steel hex socket flat point set screw — gb/t 77 / iso 4026 (series 021) require a coating for corrosion protection. Zinc plating (with or without passivation) is the most common; hot-dip galvanizing is used for outdoor structural service; black-oxide is mainly a tarnish-prevention finish for tool-room use.
Comparable Grades
For Hex Socket Flat Point Set Screw — GB/T 77 / ISO 4026 (Series 021), class 8.8 is the comparable strength step. Move up when the joint preload approaches the proof load of the current class; move down when the joint is over-specified. For corrosion-critical service, switch to stainless A2 or A4.
Sizes of Hex Socket Flat Point Set Screw — GB/T 77 / ISO 4026 (Series 021) Available in Grade 12.9 Steel
| Size | Pitch (mm) | Length L (mm) | Hex socket s (mm) | Engagement depth t min (mm) | Point diameter dp (mm) | Reference standard |
|---|---|---|---|---|---|---|
| M3 | 0.5 | 6 | 1.5 | 1.4 | 2.0 | ISO 4026-4029 / GB/T 77-79 |
| M4 | 0.7 | 6 | 2.0 | 2.0 | 2.5 | ISO 4026-4029 / GB/T 77-79 |
| M5 | 0.8 | 7 | 2.5 | 2.5 | 3.5 | ISO 4026-4029 / GB/T 77-79 |
| M6 | 1.0 | 9 | 3.0 | 3.0 | 4.0 | ISO 4026-4029 / GB/T 77-79 |
| M8 | 1.25 | 12 | 4.0 | 4.0 | 5.5 | ISO 4026-4029 / GB/T 77-79 |
| M10 | 1.5 | 15 | 5.0 | 5.0 | 7.0 | ISO 4026-4029 / GB/T 77-79 |
| M12 | 1.75 | 18 | 6.0 | 6.0 | 8.5 | ISO 4026-4029 / GB/T 77-79 |
| M16 | 2.0 | 24 | 8.0 | 8.0 | 12.0 | ISO 4026-4029 / GB/T 77-79 |
| M20 | 2.5 | 30 | 10.0 | 10.0 | 15.0 | ISO 4026-4029 / GB/T 77-79 |
| M24 | 3.0 | 36 | 12.0 | 12.0 | 18.0 | ISO 4026-4029 / GB/T 77-79 |