carbon-steelISO 898-1
Property Class 8.8
The most common engineering grade. Medium carbon steel, quenched and tempered.
Tensile Rm800 MPa
Yield Rp0.2640 MPa
HardnessHRC 22–32
Nut class8
Mechanical properties
- Property class
- Property Class 8.8
- Defined in
- ISO 898-1
- Tensile strength Rm (min)
- 800 MPa
- Yield strength Rp0.2 (min)
- 640 MPa
- Hardness
- HRC 22–32
- Matching nut class
- 8
- Material
- Carbon Steel
Where this grade is used
The property class is stamped on the head of bolts and screws of M5 and larger, so an 8.8 bolt is marked 8.8. A Property Class 8.8 fastener is specified where the joint needs a 0.2 % proof strength of about 640 MPa or less. Always pair it with a nut of ISO 898-2 class 8 or higher, so the bolt fails before the thread strips.