The term "fasteners" encompasses a tremendous number of different items-bolts, studs, nuts, screws, and rivets to name a few of the more common ones. Here we will deal with the nuts and bolts common to building a race car.
The bolt on the top is a grade...
The bolt on the top is a grade 8; the one on the bottom is a grade 1. The grade 1 failed at 44 percent of the torque of the grade 8.
As you can see in the top photo, a bolt is not necessarily a strong bolt. The bolt on the bottom has a smooth head. This categorizes it as a grade 1 or grade 2 bolt-the weakest of bolts. These are not bad, they are just designed for low-strength applications.
The bolt on the top is a grade 8 fastener; it is much stronger. You can see that both the grade 1 and the grade 8 are broken. What is not readily apparent is the torque required to break each one of them.
I used two nuts locked together on each of the two bolts. With each clamped in a vise, I used my trusty torque wrench to destroy them. The grade 1 bolt withstood less than half the pressure of the grade 8 before it snapped off. This means that it holds less than half as much torque load as the grade 8.