Nuts are often shared with screws of the same size to fix related joints.
When designing with nuts and bolts, grades and property classes of hardware should match.
However, higher strength nuts may be used with lower strength bolts.
The nut must always be stronger than the bolt for safe and proper joint design, so using a lower strength nut with a higher strength bolt is asking for trouble.
for example：Class 10 nuts are intended for use with screws and bolts of property classes 10.9 and lower.
Metric Nut Class --- Metric Bolt Class
5 --- 5.8
6 --- 6.8 They are the most popular nut for use with metric machine screws.
8 --- 8.8 They are widely used in the automotive and electronics industries.
9 --- 9.8
10 --- 10.8 They are widely used in farm equipment.
12 --- 12.8