What is the non-standard screw?

Update:12-07-2018
Summary:

Non-standard screws are the specifications that are not […]

Non-standard screws are the specifications that are not included in the national standard. They are special sizes and are generally used for applications with fewer parts.
The screw is a tool that uses the physics and mathematical principles of the circular rotation of the object and the frictional force to gradually tighten the object. Screws are a general term for fasteners

The national standard refers to the standard issued by the national standardization authority, which is of great significance to the national economic and technological development and is unified throughout the country. The national standard is a unified technical requirement across the country. The standardization administrative department of the State Council prepares the plan, coordinates the division of labor, organizes the formulation (including revision), and uniformly approves, numbers, and issues. The law provides for the establishment of national standards.

The national standard refers to the pitch size specified in the national standard, and the non-standard is the pitch size determined according to the needs or user requirements. In addition, the inch system and the US system can also be called non-national standards.

Screws, also known as "screws" [Screw] (screws), "screws" (screws). In fact, the screw is a general name, and the screws and screw rods are different from each other. Screws are generally called wood screws; they are the ones with pointed ends on the front end, and the pitch is large, which is generally used to fasten wooden parts and plastic parts. The screw rod is a machine screw (mechanical screw), which is the kind of flat head at the front end. The pitch is small and uniform, and it is generally used to fasten metal and machine parts.