How to distinguish the quality of screw bolts?

What are the differences between bolts and screws?
There is an assumption that screw bolts are screws that they are the same fastening hardware. While they look similar and even have similar characteristics, they are two unique fasteners with their own unique applications.

Screw bolts are used to assemble to unthreaded objects with nuts. Screws assemble objects with threads. Some objects have pre-made threads, whereas others create the thread during the installation. The screw bolt is to assemble threaded objects, while the screw is to assemble untreaded objects.

Screws must be turned to assemble a joint, while screw bolts can be secured in place using a tool. Screw bolts are typically used to make a bolted joint by using a nut to apply force while using the shank to act as a dowel. This pins the joint against sideways forces. Therefore, many screw bolts have an unthreaded shank, making them more effective for dowels.

How to distinguish the quality of screw bolts?
First of all, screw bolts have to look at the material before they are made. Quality compliance is the prerequisite for reaching the national standard. Without looking at the material, the heavier one is the better

Then look at the tolerance value between the screw bolts and the national standard. The standard is used to determine whether it is good or not. The smaller the tolerance value of screw bolts and national standards, the better screw bolts are. After screwing the nut into the screw bolt, hold the nut and shake it left and right to feel the gap between the nut and the screw bolt. The one that has the larger gap is inferior. This way can check the rib accuracy of the screw bolt.