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Fasteners necessary screw knowledge treasure book, worth collecting!
Time：
2024-12-18
Countersunk head screws, also known as flat machine screws, flat head screws, its head is a 90-degree cone, the surface of the mounting holes in the connector is also processed with a 90-degree cone nest, so as to ensure that the head of the screw and the connector surface parallel to the surface of the screws and is used for the surface of the surface can be allowed to protrude a little place.
Countersunk head screws commonly used KM, FM, KA and so on.
1. The thickness of the parts to be fastened is greater than the thickness of the head of the countersunk head screws, after the screw is tightened, there is still a part of the screw threads do not enter the threaded hole. In this case, the countersunk head screws can certainly be tightened.
2. The thickness of the parts being fastened is less than the height of the head of the countersunk head screws, which is common in mechanical equipment in the sheet metal parts, such as chassis hinges and the door and the box connection; equipment sheet metal cover and equipment connection and so on. Due to the small thickness of the parts, the sheet metal parts being fastened, the screw over hole completely into a conical hole, in this case, when the countersunk head screws are tightened, the head of the screw is not a conical surface compression of the sheet metal parts, but the bottom of the root of the head of the screw with the top of the threaded hole squeezed to death, although it feels that the screws are tightened, but the sheet metal parts are jammed rather than pressed, in this case, although it feels that the screws are tightened, but the In this case, although the screw is felt to be tightened, the sheet metal part is really not tightened. This is a very common situation.
3. countersunk head screws head vertebrae 90 ° cone angle, usually bought a new drill top angle of 118 ° - 120 °, some lack of training workers do not know the angle difference, often directly with 120 ° of the drill reaming, which results in countersunk head screws tightening is not the head of the conical surface of the force, but the bottom of the screw head of a line of force, which is also known as the so-called countersunk screws can not be tightened for one of the reasons. One of the reasons why the so-called countersunk head screws can not be tightened.
