When using screws, it is better to understand their mechanical properties first, as different types of screws have varying mechanical properties, which in turn determine the appropriate usage scenarios.
1. Self-tapping screw: mechanical performance requirements
1. Core hardness: The standard value ranges from 240 to 425HV. The test should be conducted on a cross-section located 1-2 times the diameter away from the tail end. If the tail end is too short, it can be embedded first, and then the hardness can be measured.
2. Surface hardness: standard MIN HV450.
3. Carburized layer: Standard 4#-6#: 0.05-0.18mm, 8#-12#: 0.10-0.23mm, 14#: 0.13-0.28mm. The main purpose of carburizing is to enhance surface hardness and ensure the strength of the tooth. If the decarburization is too deep and the carburizing is insufficient, the strength of the tooth will not meet the requirements, which means that the tooth will be damaged during the screwing test.
4. Torque: Standard specifications include 4#, 5#, 6#, 7#, 8#, 10#, 12#, 14#, A thread sizes of 1.5, 2.8, 3.4, 4.5, 6.5, 6.5, 10, and 14
5. Screw-in test: Screw the self-tapping screw into a steel plate with a reserved test hole. The self-tapping screw should form a matching thread within the test plate, without any deformation or damage to the thread of the screw itself, until the end taper thread completely passes through the test plate. The screw-in test is only applicable to self-tapping screws of types AB, B, BP, etc. According to IFI regulations, the test plate should be made of semi-hard low-carbon cold-rolled steel with a Rockwell hardness of 70–85 HRB. The standard specifications for the steel plate, including thickness, are shown in the table below. The test hole should be punched or drilled, with a tolerance of ±0.025mm from the specified nominal diameter (see table below). Specification 6#7#8#10#12#1/4 Test plate thickness (mm) 1.85-1.95 3.12-3.23 4.68-4.84 Hole diameter (mm) ±0.025 2.95 3.26 3.45 4.04 4.76 5.50.
II. Wallboard nail
1. Core hardness: Standard: 240--425HV.
2. Surface hardness: Standard: HV600-800.
3. Carburized layer: 4#-6# 0.05-0.18mm, 8#-12# 0.10-0.23, 14# 0.13-0.28.
4. Bending degree: required to be 150 -450
5. Salt spray test: generally, it is a minimum of 48 hours.
6. Torque: Specifications 6#, 7#, 8#, 10# with torques of 2.8, 3.4, 4.5, 6.5, 6.5
III. Drill tail screw
1. Core hardness: Standard: 240--425HV
2. Surface hardness: Standard: HV600-700. Our company's products are measured to have a surface hardness of around HV620.
3. Hardened layer: 4#-6#: 0.05-0.18mm 8#-12#: 0.10-0.23mm 14#: 0.15-0.28mm
4. Torque: specifications, drill tail, screw, ST2.9 (4#) 1.5, ST3.5 (6#) 2.8, ST3.9 (7#) 3.4, ST4.2 (8#) 4.5, ST4.8 (10#) 6.5, ST5.5 (12#) 10, ST6.3 (14#) 14
