Steel Thread Cutting Screw

The screws are carburized and quenched. A hard and wear-resistant carburized layer is formed on the surface. The surface hardness reaches 450~650 HV (approximately 48~56 HRC). This is enough to easily cut regular carbon steel plates. Take ST3.5 as an example. Its surface hardness has been measured up to 580 HV. In the test of repeated screwing in and out, there was no obvious wear on the thread cutting edge. This guarantees consistent cutting results during series assembly.

Various cutting groove designs such as D-type, F-type, and T-type are available. They are respectively targeted at different substrates such as metal sheets, plastics, and wood. For example, type D has 2 to 3 longitudinal grooves. When used for steel plates with a thickness of 0.8 to 2.0 mm, the recommended bottom hole diameter is 3.3 to 3.4 mm (ST4.2). Test data shows that screwing-in torque can be reduced by 30% using the correct type. It can also prevent plastic parts from cracking due to excessive extrusion stress.

Various head types such as pan head, countersunk head, and hexagonal flange are available. Length range covers 4 mm to 100 mm. This can adapt to different plate thickness and countersunk head requirements. For example, ST4.2 pan head screws are available in lengths from 8 mm to 50 mm. It can join various combinations of 1.0 mm steel plates and 6 mm plastic parts. Statistics show that flexible matching of specifications and lengths can increase design selection efficiency by 40%. It also reduces additional customization costs.

The coating thickness of the screw head, shaft and thread groove edge directly affects the rust prevention ability. Use X-ray fluorescence thickness gauge for detection. The coating thickness ratio of the thread crest to the thread bottom of high-quality screws is not less than 0.7. The average thickness is 8~12 μm. Take ST3.5 as an example. The crest coating is 9.5 μm. The tooth base coating is 7.2 μm. The ratio between the two is 0.76. The ratio of general products is often lower than 0.5. This results in exposed edges of the cutting grooves. In the salt spray test, red rust first appeared from the groove. Its anti-rust life is thus shortened by half.

Can be used with pre-installed sealing rings

• The head can be pre-installed with nylon gaskets or O-rings. The sealing pressure reaches 0.3 MPa and the waterproof grade is IP67. The separate gluing process is omitted, and the single-piece assembly time is reduced by another 2 seconds.

Thread start optimization

• The taper at the starting end of the thread is designed to be 15°~20°. The success rate of entry hole alignment is increased to 99.5%. Compared with right-angle starting ends, the jamming rate is reduced by 70%, significantly reducing rework.

Avoid the risk of nuts falling off

• Nutless design, there is no problem of nut vibration loosening or losing. According to on-site statistics, the rework rate due to nut falling off has been reduced to less than 0.1%. Reliability is significantly improved.

Reduce substrate deformation

• The radial extrusion force generated during the cutting process is only 40% of that of the extrusion type. Taking the ST3.5 connection to a 0.8 mm thin plate as an example, the back protrusion height is reduced from 0.3 mm to 0.1 mm. Smoother appearance.