Recently, there was a small friend’s private letter from the small editor of the Olympic Exhibition asking how to distinguish wood screws from self-tapping screws, and he took the opportunity to introduce it to you. Fasteners can be divided into three categories according to the form of thread. External thread fasteners, internal thread fasteners, non-threaded fasteners, wood screws and self-tapping screws are all external thread fasteners.
Wood screw is a kind of screw specially designed for wood, which can be directly screwed into the wooden component (or part) to firmly connect a metal (or non-metallic) part with a through hole with a wooden component. This connection is detachable. There are seven kinds of wood screws in the national standard, which are slotted round head wood screws, slotted countersunk head wood screws, slotted half-countersunk head wood screws, cross recessed round head wood screws, cross recessed countersunk head wood screws, cross recessed half-countersunk head wood screws, and hexagonal head wood screws. The more commonly used is cross recessed wood screws, and the cross recessed countersunk head wood screws are the most widely used among the cross recessed wood screws.
After the wood screw enters the wood, it can be very firmly embedded in it. It is impossible for us to pull out the wood without decay. Even if you pull it out forcibly, it will damage the wood and bring out the nearby wood. Therefore, we need to use tools to screw out the wood screws. Another thing we need to pay attention to is that the wood screw must be screwed in with a screwdriver, and the wood screw cannot be forced in with a hammer, which is easy to damage the wood around the wood screw, and the connection is not tight. The fixation capacity of wood screws is stronger than that of nailing, and it can be replaced without damaging the wood surface. It is more convenient to use.
The thread on the tapping screw is a special tapping screw thread, which is usually used to connect two thin metal components (steel plate, saw plate, etc.). As the name implies, the self-tapping screw can be tapped by itself. It has high hardness and can be directly screwed into the hole of the component to form the corresponding internal thread in the component.
The self-tapping screw can tap the internal thread on the metal body to form thread engagement and play a fastening role. However, due to its high thread bottom diameter, when it is used for wood products, it will cut into wood shallowly, and because of the small thread pitch, the wood structure between each two threads is also less. Therefore, it is unreliable and unsafe to use self-tapping screws for wooden mounting parts, especially for loose wood.
The above is the introduction of wood screws and self-tapping screws. I hope it can help you distinguish wood screws and self-tapping screws. In short, the thread of wood screw is deeper than that of self-tapping screw, and the spacing between threads is also larger. The self-tapping screw is sharp and hard, while the wood screw is sharp and soft.