The following items introduce the knowledge of combined screws in detail:
1. Combined screw forming self-tapping screws A, AB, B, BP, C and other types are now gradually replaced by combined screws rolled into self-tapping screws, so it is not recommended to use them in the new plan. AB, B, BP are different Only in the tail shape, AB has a combined screw cone tail,
2. B has a blunt tail, BP has a cone tail without a combination screw, and the pointed tail base enters the pre-drilled hole and preliminarily forms the combination screw. The combination screw cutting self-tapping screw has BF, BP, D, F, G and T In other methods, BF and BP are wide combination screws, and the rest are mechanical combination screws.
3. The difference in identifying characters lies in the cutting tail. Each cutting tail has a shape that can collect the scraps from the cutting. Assuming that the self-tapping screw is screwed into the blind hole (the hole that does not penetrate), the fragments will remain and be sealed At the bottom of the hole.
4. But if the through hole is tapped, the waste will fall on the other side of the workpiece. Therefore, this type of self-tapping screw must be considered when selecting this type of self-tapping screw. The waste may form pollution and fall into the working parts or make the electronic substrate Can't work.
  5. All combination screws rolled into self-tapping screws are mechanical combination screws, which are the same as British and American common combination screws. Please refer to SAE J81 rules. For metric combination screws, please refer to SAE J1237 and DIN7500 rules.