Identification and selection: flat head screws, countersunk head screws, round head screws

The screw is a tool that uses the physics and mathematics of the oblique circular rotation of the object and the friction force to gradually tighten the objects and parts. In the classification of plastic screws, we will find interesting classifications such as flat head, countersunk head, and round head screws. For example, there is such a difference in the screw classification, so what is the difference between these three types of screws?

Summary is as follows:
From the appearance point of view: the head of the flat head screw is flat, and the surface of the screw is parallel to the surface of the fastening object after the fastener is screwed in; the countersunk screw is also called the flat machine screw, which is similar to the flat head screw. They are all flat, but the difference is that there is a 90-degree cone under the head plane; the round head screw is very different from the above two screws. The semi-circular head of the fastener is protruding.

As far as the characteristics of these three kinds of screws are concerned, the force of flat head screws can be greater than that of countersunk head screws, flat head screws can be added with flat washer spring washers, and countersunk head screws can only be added with taper washers. But grub screws can be exposed or in the counterbore, while countersunk screws are generally only in the counterbore. The force of the round head screw is less than the above two types, and the fastening strength is not as great as the above two types, but it is very convenient for disassembly because of the protruding head.

From the point of view of the purpose of the screw, the slot of the head of the flat head screw generally has: cross groove, inner hexagon, plus and minus groove, hexalobular groove, slot and other grooves. It is mostly used in construction projects with high strength and power dispatching; countersunk screws have a flat, cross, and hexagon socket. From the perspective of flat grooves, flat head screws and countersunk screws have significant similarities. The scope of application of countersunk screws is also in construction engineering, machinery industry and so on. And the order expression method uses letters instead of KM, FM, KA; the big difference is the round head screw, which generally only has a slotted groove. Round head screws are generally used for projects that allow exposure and tend to require easy disassembly.

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