There are seven main points about the types of screws:

1. Slotted screws are usually used for joining smaller parts. It has pan head screws, cylindrical head screws, semi-countersunk head screws and countersunk head screws. The head strength of pan head screw and cylindrical head screw is high, and the shell is connected with the general parts; The head of the half-countersunk head screw is curved, and its top is slightly exposed after installation, and it is beautiful and smooth. It is generally used for instruments or precision machinery; Countersunk screws are used where the nail head is not allowed to be exposed.

2. The head of hexagon socket and hexagon socket torx screw can be embedded in the component, which can exert large torque and has high connection strength, and can replace hexagon bolt. It is often used at joints with compact structure and smooth appearance.

3. The general screw with cross slot has the same application function as the general screw with slot, and can be replaced with each other. However, the general screw with cross slot has higher groove strength, is not easy to screw out, and has a beautiful appearance. When in use, the supporting cross screwdriver must be used for loading and unloading.

4. The eyebolt eyebolt is a kind of hardware accessory for the device and transportation. During application, the screw must be screwed into the position that makes the bearing surface close to each other. It is not allowed to use tools to tighten it, nor is it allowed to have the load effect perpendicular to the plane of the lifting ring on it.

5. Set screw Set screw is used to fix the relative orientation of the parts. Screw the set screw into the screw hole of the part to be tightened, and press its end tightly on the surface of another part, that is, fix the former part on the latter part. The set screw is generally made of steel or stainless steel, and its end shapes are conical, concave, flat, cylindrical and stepped. The end of set screw with cone end or concave end directly presses the part, which is generally used at the place where it is not often disassembled after the device; The end of the flat-end set screw is smooth and does not damage the appearance of the part after tightening. It is used at the joint where the orientation needs to be adjusted frequently, and can only transmit a small load; The fixed screw part at the cylindrical end is often used to adjust the fixed position. It can bear a large load effect, but the anti-loose function is poor. When it is fixed, anti-loose measures should be taken; Stepped set screws are suitable for fixing parts with large wall thickness.

6. Self-tapping screw When the self-tapping screw is used on the connected part, the connected part can not be pre-threaded. During connection, screw out the thread directly. It is often used to connect thin metal plates. There are two kinds of tapping screws: taper end tapping screw and flat end tapping screw.

7. Self-tapping locking screw Self-tapping locking screw not only has self-tapping effect, but also has the function of low screw-in torque and high locking. Its thread is of triangular cross-section, and the surface of the screw is hardened, with high hardness. Its thread standard is M2 ～ M12