What kinds of screws are most commonly used in standard parts and which models are the most common?

Screw is a tool to tighten instruments and parts step by step by using the physical and mathematical principles of circular rotation and friction of the inclined plane of an object. Screw is a general term for fasteners. Screws are indispensable industrial necessities in daily life, such as tiny screws used in cameras, glasses, clocks and watches, electronic products, etc. Universal screws for TV sets, electrical products, musical instruments, furniture, etc. As for projects, buildings and bridges, large screws and nuts are used; Transportation equipment, airplanes, trams, cars, etc. There are both large and small screws. Screw plays an important role in industry. As long as there is industry on the earth, the role of screws will always be important. Screw is the same invention in people's production and life for thousands of years. According to the application field, it is the first invention of mankind.

General specification

Answer: Metric screws

B: American screws C: English screws

Answer: Metric mechanical screws: Metric.

Example: M3 x 6-PP B:M3 machine screw, 6mm long, cross-shaped, round head, black plated.

Finishing code: appearance treatment specification

Head code: head shape

Thread code

Screw model driving code: head grooving, characteristic model.

Length code: screw length (mm)

A- 1: thread code: screw model.

Metric screws directly indicate the screw model with the external diameter of the screw.

Such as M3, that is, the outer diameter of the screw is 3.00mm；; M4 means that the outer diameter of the screw is 4.00 mm. 。

Metric thread size x pitch:

Note: Metric screws are behind the screw model, and sometimes the pitch is indicated.

Such as M3X0.5, M4x0.70, M5x0.8, M6 x 1.

However, due to standard specifications, it is usually not mentioned.

A-2: length code: screw length:

Metric screw, directly indicating the length of the screw, in millimeters.

Displays the total length of the screw, and only calculates the length below the screw head, excluding the height of the screw head.

Except flat head screws, the total length of screws includes the height of screw head.

A-3: driving code/head groove, characteristics.

Ordinary coarse thread: feature code M+ nominal diameter+rotation direction+thread tolerance zone code (pitch diameter, top diameter)-tightening length.

Ordinary fine thread: feature code M+ nominal diameter * pitch+thread direction+thread tolerance zone code (pitch diameter, top diameter)-thread length.

The right-hand thread is omitted, and the left-hand thread is represented by "LH".

M 16-5G6g stands for common thread with coarse teeth, with nominal diameter of 16 and right hand rotation. The thread tolerance zone has a median diameter of 5g and a major diameter of 6g, and the screwing length is regarded as medium length.

M 16× 1LH-6G represents fine thread, with nominal diameter 16 and pitch 1, left-handed. The middle and large diameters of the thread tolerance zone are 6g, and the screwing length is considered as medium length.