After so many years of doing machinery, you certainly don’t know the meaning of the screw mark, right?
The performance grade of bolts for steel structure connection is divided into more than 10 grades, including 3.6,4.6,4.8,5.6,6.8,8.8,9.8,10.9,12.9. The bolts of class 8.8 and above are ma...
Read more