Screw is an incorrect name, which is a general term for threaded parts by non-professionals, and there is no such term in the industry.
In the fastener industry, in fact, there is no strict distinction between screws and bolts. However, within the industry there are two ways to differentiate between screws and bolts:
1. According to the wrench structure. The so-called wrench structure refers to the place where the wrench is placed on the screw/bolt. That is to say, in some systems, the externally threaded rod-shaped parts of the external wrench structure are used. They are collectively called bolts, and conversely, those with internal wrenching structures are called screws. External wrench structure: hexagon head bolt; internal wrench structure: hexagon socket head bolt, etc. This is a more obvious example of fasteners in Chinese national standards, for example, GB5782, GB5783 (one half thread, one full thread) . Because they are all hexagonal structures, in the standard name, they are all called: bolts.
2. Distinguish according to whether the product has non-threaded rod features. This is also a widely used classification method, which is generally used to distinguish bolts and screws
. That is: if all the stems of the product except the head are threaded, this part is called a screw. On the other hand, if, in addition to the thread, it also has the characteristics of a polished rod, it is called a bolt.