Generally refers to the pointed, coarse teeth, hard texture of the wood screws, but also for aluminum, plastic. A special small screw used for metal hole threading is called wire tapping.
Stainless steel screws Surface treatment: Most of the self-tapping screws are coated with galvanized or zinc phosphate. Cadmium is used because of its high cost and toxicity. If the appearance is important, nickel or Chrome. Appearance disposal will be issued two questions: one is that the appearance of the disposal will not only increase the scale (such as the reduction of the hole, etc.) and the appearance of different treatment will affect the torque, tightness, strength between the links, so in the The test should be made according to galvanized, cadmium or phosphate treatment to do the same rules in the test for drilling diameter, the use of stainless steel screws must be the same appearance of the disposal of the screw. The second is, high hardness , Self-tapping screws are often due to hydrogen embrittlement caused by the use of self-tapping screws in order to attack into the iron plate, had to carburizing treatment in the carburizing treatment will be issued after the high hardness and high carbon content, This is the case of electroplating or pickling treatment will occur when the hydrogen embrittlement.Specifically advocated to eliminate the hydrogen embrittlement method is: a). Plating or pickling within 1 hour after the implementation of baking. B). Temperature 375 ~ 425 oF (190 ~ 220 oC). At least 4 hours.
Hydrogen embrittlement test: hydrogen embrittlement test is mainly to test the self-tapping screw is not the residual hydrogen in the screw arrangement and is not to make self-tapping screws hair embrittlement, (usually brittle fracture is not a moment to attack, and must be given The stress will be apparent) plating or drape of the screws should be charged in the rules of Table 3, such as the test plate and steel Pinghua Division, the outstanding head type screw head under the use of standard Pinghua Division, buried (Oval) screws are fitted with chamfering distance steel plates. The thickness of the flat surface or the distance from the sheet should fit the maximum tooth length of the screw. The handle can be supported by a longer cold-rolled steel sheet or flat weave to ensure that the complete part of the tooth can be knotted and maintained in the thickness of the test iron plate. The stainless steel screw should be locked to 80% of the maximum breaking torque , Breaking the torque is to lock the five screws to break with its average resolution, continue to adhere to the lock to continue after 24 hours, then screw the screw and then spin to the original locking torque, the screw should be no significant defeat.