Markings such as 6.8, 8.8 or 10.9 on a bolt head show its property class according to ISO 898-1. Choosing the right class directly affects the strength and service life of the furniture.
What do the two numbers mean?
The first number is one hundredth of the nominal tensile strength (N/mm²). The second gives the ratio of yield strength to tensile strength in tenths. An 8.8 bolt therefore has about 800 N/mm² tensile strength and about 640 N/mm² yield strength.
| Class | Tensile (≈ N/mm²) | Yield (≈ N/mm²) |
|---|---|---|
| 4.8 | 400 | 320 |
| 6.8 | 600 | 480 |
| 8.8 | 800 | 640 |
| 10.9 | 1000 | 900 |
Which class for furniture?
- 6.8: wooden frame joints, carriage bolts and studs — the most common class in furniture.
- 8.8: mechanism assembly, metal frames and load-bearing joints.
- 10.9: high-torque socket and set screws, machine parts.
Use a nut whose class is at least the first number of the bolt (class 8 nut for an 8.8 bolt). Browse our bolts.
Need help choosing?
Get a Quote
Contact our team for quotes, samples and technical details.