Basic knowledge of screws

- Aug 24, 2020-

1. Terms related to screws

●The difference between screws, screws, bolts and fasteners.

●Definition of thread: a thread is a shape with uniform spiral lines on the outer or inner surface of a solid.


2. The role of thread

●Tightening and connection function: suitable for most screw products at this stage.

●Transmission function (displacement function): such as a micrometer used for QC check size.

●Sealing function: such as the connection of pipelines.

3. The history of thread development


Machine Screw→Self Tapping Screw→Self Drilling Tapping Screw.

●Machine thread: When assembling, drill holes and taps on the assembly first, and the inner teeth of the tapping are the same as the outer teeth of the screw. Use a smaller torque to assemble.

●Self-tapping thread: When assembling, drill holes in the assembly first, without tapping the internal teeth, use a larger torque for assembly.

●Self-drilling thread: directly used on the assembly, the screw is drilled and tapped once.

4. Screw processing method

●Turning: By removing the material, the material reaches the desired shape.

Advantages: high processing accuracy, no mold restrictions.

Disadvantages: high production cost and slow processing speed.

●Forging: Extruding the material by external force to deform it to achieve the desired shape.

Advantages: fast production speed, low cost, suitable for mass production.

Disadvantages: Molding is limited by molds, and mold costs for complex products are high.

5. Cold heading process

●Cold heading: is the process of using a mold to squeeze and deform the metal wire with the help of external force when the metal wire is not heated.

●The cold heading process is only one of the forging processes.

6. Raw materials commonly used in manufacturing screws

●Metal and non-metal.

●Metals: iron Fe, copper Cu, aluminum AI.

●Iron: Carbon Steel, Alloy Steel, Stainless Steel.

●The shape of the raw material (wire and bar).

●The processing technology of raw materials.

●Current source of metal materials: Japan/Korea, Taiwan, Mainland China.

7. Screw standard

●National standard: GB-National Standard, BS-British Standard.

●Industry standards: SAE-American Society of Automotive Engineers, AISI-American Iron and Steel Institute, JCIS-Japanese Camera Industrial Standard, DIN-German Industrial Standard JIS-Japanese Industrial Standard.

●Enterprise standard: GE-General Motors Standard, IBM Standard, SONY Standard

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