Types Of Screws

Screw refers to a screw. It is a tool that uses the physical and mathematical principles of the circular rotation and frictional force of an object to tighten objects and objects in order. Screws are a common term for fasteners, and they are spoken everyday.

The metric thread is in MM (millimeters) and its cusp angle is 60 degrees. Both American thread and inch thread are in inches. The tip angle of the American thread is also 60 degrees, while the tip angle of the English thread is 55 degrees.


1) Slotted common screws

Mostly used for connection of smaller parts. It has pan head screws, cylindrical head screws, half countersunk head screws and countersunk head screws. The heads of pan head screws and cylindrical head screws have high strength, and they are connected to ordinary parts; the head of the semi-counter head screw is curved. After installation, its top is slightly exposed, and it is beautiful and smooth. On precision machinery; countersunk head screws are used where the nail heads are not allowed to be exposed.

2) Hexagon socket head cap screws

The head of this type of screw can be buried in the component, which can apply a large torque and high connection strength, and can replace the hexagonal bolt. Commonly used in joints that require compact structure and smooth appearance.

3) Cross recessed common screw

It is similar to the use function of slotted ordinary screws, and can be replaced by each other, but the groove strength of the cross-slotted ordinary screws is high, it is not easy to twist, and the appearance is more beautiful. When using it, you must use the matching cross-shaped screwdriver for loading and unloading.

4) Eye bolt

The eye bolt is a kind of hardware fitting for bearing during installation and transportation. During use, the screw must be screwed into a position that makes the support surface closely fit. It is not allowed to use a tool to tighten it, nor is a load perpendicular to the plane of the ring allowed to act on it.

5) Set screw

Set screws are used to fix the relative position of the machine parts. Screw the set screw into the screw hole of the part to be tightened, and press the end of the set screw against the surface of the other part, that is, fix the former part on the latter part.

The set screw is usually made of steel or stainless steel, and its end shape is tapered, concave, flat head, cylindrical and stepped. The end of the set screw at the tapered or concave end directly presses the part, generally used for the place where it is not often disassembled after installation; the end of the set screw at the flat end is smooth, and the surface of the part is not damaged after the tightening, used for frequent adjustment of position Only small loads can be transmitted at the joints; the fixed screw part at the cylindrical end is used to adjust the fixed position frequently. It can withstand larger loads, but the anti-loosening performance is poor, and anti-loosening measures are required when fixing; Set screws are suitable for fixing parts with large wall thickness.

6) Self-tapping screws

When self-tapping screws are used on the connected parts, the connected parts may not be pre-made with threads. When connecting, the screw is used to tap the thread directly. It is often used to connect thin metal plates. There are two types of taper-end self-tapping screws and flat-end self-tapping screws.

7) Self-tapping screw

Self-tapping locking screws not only have the function of self-tapping, but also have the performance of low screw-in torque and high locking. Its thread has a triangular cross-section, and the surface of the screw is hardened and has a high hardness. Its thread specifications are M2 ~ M12

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