MECHANICAL PROPERTIES OF BOLTS AND NUTS
The ISO metric system (International Organization for Standardization) is one of the most widely used measurement systems in the world, particularly in industrial and engineering applications. A fundamental part of the ISO system includes bolts and nuts, which are essential for assembling various mechanical components. This document analyzes the mechanical properties of bolts and nuts according to ISO standards, including tables, graphs, and illustrative images.
Mechanical Properties of ISO Bolts
ISO bolts are classified based on their nominal diameter (M) and thread pitch. Common strength classes for steel bolts include 8.8, 10.9, and 12.9, which indicate the tensile strength and yield strength of the bolts. The following table shows the mechanical specifications for class 8.8 bolts:
| Strength Class | Tensile Strength (N/mm²) | Yield Strength (N/mm²) |
| 8.8 | 800 | 640 |
| 10.9 | 1000 | 900 |
| 12.9 | 1200 | 1080 |
The table below represents the relationship between applied force and elongation for a class 8.8 bolt:
Mechanical Properties of ISO Nuts
ISO nuts are designed to withstand the same forces as the bolts they are paired with. The strength of nuts is generally specified according to the strength class, as shown in the following table:
| Strength Class | Tensile Strength (N/mm²) |
| 8 | 800 |
| 10 | 1000 |
| 12 | 1200 |
The following table illustrates the types of stress a nut undergoes when tightened onto a bolt:
Performance Analysis
The performance of a bolt-nut assembly depends not only on the individual characteristics of each component but also on factors such as proper tightening torque and operating conditions. Selecting the appropriate strength class is crucial for ensuring safety and reliability in mechanical joints.
| Bolt-Nut Combination | Maximum Load (kN) | Operational Safety |
| Bolt 8.8 - Nut 8 | 64 | High |
| Bolt 10.9 - Nut 10 | 90 | Very High |
| Bolt 12.9 - Nut 12 | 108 | Exceptional |
Conclusion
ISO bolts and nuts are essential components in numerous industrial applications, thanks to their standardization and mechanical reliability. Selecting the correct bolt-nut combination can significantly impact the performance and safety of mechanical structures.
From a business perspective, adopting ISO bolts and nuts simplifies inventory management, improves the quality of finished products, and reduces maintenance costs.
Implementing these standards is a strategic choice for companies aiming to enhance production efficiency and deliver high-quality products. Investing in ISO-standardized components also provides customers with the assurance of compliance with international regulations, a key factor for success in global markets.