What is a Screw, a Detailed Introduction to the Screw!


Introduction to the Screw

Screws are tools that use the physics and mathematical principles of the circular rotation and friction of the bevel of an object to gradually tighten the components of the object.

Screws are indispensable industrial essentials in daily life: extremely small screws for cameras, glasses, clocks, electronics, etc.; general screws for televisions, electrical products, musical instruments, furniture, etc.; for engineering, construction, and bridges, large Screws, nuts, transportation equipment, airplanes, trams, cars, etc. are used for both size and size.

Screws have an important task in the industry. As long as there is industry on the earth, the function of the screw is always important. Screws are the common inventions in people's production and life for thousands of years. According to the application field, it is the first invention of human beings.


A Brief History of the Invention of Screws

1. The first person to describe the spiral was the Greek scientist Archimedes (circa 287 BC - 212 BC). The Archimedes spiral is a huge spiral mounted in a wooden cylinder that lifts water from one level to another and irrigates the field.

2. In the Middle Ages, carpenters used wooden nails or metal nails to connect furniture to wooden structures. In the 16th century, nailers began to produce nails with spirals that could connect things more securely. That is a small step from this type of nail to the screw.

3. It appeared in London around 1780. Carpenters found that screwing a screw with a screwdriver can fix things better than a hammer, especially when it comes to fine-grained screws.

4. In 1797, Mozley invented the all-metal precision screw lathe in London. The following year, Wilkinson made a nut and bolt making the machine in the United States. Both machines produce universal nuts and bolts. Screws are quite popular as fixed parts because an inexpensive production method has been found at that time.

5. In 1836, Henry M. Philips applied for a patent for the screw of the cross recessed nailhead, which marked a significant advancement in the screw base. Unlike conventional slotted head screws, the Phillips head screw has a Phillips head screw head edge. This design makes the screwdriver automatically centered and not easy to slip off, so it is very popular.


What Are the Materials of the Screws?


Steel screws are the most common, and they are the cheapest and can be processed on a variety of surfaces.

1. Low carbon steel C%≤0.25% is mainly used for products with no hardness requirements such as 4.8 bolts, 4-grade nuts, and small screws.

2. medium carbon steel 0.25%

3. High carbon steel C%>0.45%.

4. alloy steel: adding alloying elements to ordinary carbon steel to increase some special properties of steel

5. stainless steel. It has anti-corrosion characteristics.



Common materials are brass, zinc-copper alloy. The brass screw is the most common copper alloy, relatively inexpensive and not very strong, but helps prevent corrosion. If the screws are exposed to moist air, the copper helps ensure that the screws are durable for long periods. Its role is mainly used to decorate and beautify.



Aluminum screws, which are all screws with the same volume weight are light, non-magnetic, and also have corrosion resistance and aesthetics. It is also possible to add other metal elements such as iron, magnesium, and zinc. Aluminum alloy can obtain the same hardness as steel, so it can be used in situations where both high strength and light weight are required. Although aluminum screws are far from popular, they are used in aviation and medical related fields. Has a unique nature and its use is more and more extensive



Titanium screws have the advantages of low density, high strength, good corrosion resistance, and good process performance. They are ideal aerospace engineering structural materials. It is also the material of choice for all fasteners, but the price is also very high. Fasteners of these materials are typically used in aerospace applications.


What Are the Classification of Screws?

There are three common classifications of screws

According to the thread can be divided into

  • Self-tapping screws,
  • Mechanical screws,
  • Self-drilling screw


From the header section:

  • Pan head screw
  • Large flat head screw
  • Semi-circular head screw
  • Countersunk head screw
  • Half countersunk head screw
  • Cylindrical head screw


According to the slot type:


Standards for Screws

The international standard for screws is also called metric screw threads, and the pre-existing British standard will be replaced by the metric system. The main difference between the two standard threads is the pitch and diameter. J-Japanese (JIS) D-European (DIN) A-American (AISI) G-National Standard (GB) B-British (BSW) S-International Standard (ISO) T-Special Standard

There are two main measurement units of length in the world today. One is the metric system, and the measurement units are meters (m), centimeters (cm), millimeters (mm), etc., which are small in Europe.

China, Japan, and Southeast Asia use more, the other is the British system, the measurement unit is mainly inches (inch), in the United States, Britain and its former colonial countries used


① metric measurement :(decimal)

1 m = 100 cm = 1000 mm


② inch measurement :(Octal)

1 inch =8 FCM 1 inch =25.4mm3/8¢¢×25.4=9.52


③ Products below 1/4c have serial Numbers to indicate their title path, such as 4#,5#,6#,7#,8#,10#,12#

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