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Common standard knowledge of screws

The dimensions, mechanical properties and functional performance of self-tapping screws have the following standards
　　American National Standards Institute (ANSI)/ASME B18.6.4─Thread forming and thread cutting self-tapping screws and metal drive screws (inch series)
　　SAE J933─Mechanical and quality requirements, self-tapping screws
　　J81 screw thread rolling─SAE
　　SAE J1237─Metric thread rolling screw
　　SAE J78─steel self-tapping screws
　　FIP 1000─self-tapping screw performance specifications
　　DIN 7500─Thread Rolled Screw ISO Metric Screw Line
　　DIN 7504─Self-tapping screw size, requirement and test
　　ISO 2702─Tapp heat-treated steel
 
U.S. regulations

a. Generally marked with a serial number, such as #2-56, #4-40, #6-32, #8-32, #10-24…etc.
b. Or expressed in English outer diameter, such as 0.086-56, 0.112-40, 0.138-32, 0.164-32, 0.190-24...etc.
Ex: 632 – 8 – P P B:
Finish Code: Appearance processing specifications
Head Code: Head shape
Drive Code: head section groove, characteristic model
Length Code: Screw length
Thread Code: Screw model
B-1: Thread Code: Screw model
B-2: Length Code: Screw length (B-3, B-4, B-5: The marking method is the same as the metric system)
The length of US-standard screws must be converted to the metric mm size. Conversion formula: (Length Code / 32) x 25.40 = metric length mm

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