Fasteners-Basic Knowledge Of Screws

What is a screw?

A screw is a tool that uses the physical and mathematical principles of the oblique circular rotation of the object and the friction force to gradually tighten the objects and parts. The screw is a general term for fasteners.


Commonly used screw types:

1. Machine Screw

2. Tapping Screw

3. Sheet Metal Tapping Screw.

4. Plastic Tapping Screw.

5. Wooden Screw

6. Drywall Screw

Common screw material:

1. Low Carbon Steel

2. SS-304: Stainless Steel 304;

3. SS-302: Stainless Steel 302

4. Aluminum 5052

5. Brass

6. Bronze

7. UNS C11000 Copper

Screw structure classification

1. Slotted ordinary screws

Mostly used for the connection of smaller parts. It has pan head screws, cylindrical head screws, half countersunk head screws and countersunk head screws. The nail heads of pan-head screws and cylinder-head screws are high in strength and are connected to ordinary parts; the head of the half countersunk head screw is arc-shaped, and its top is slightly exposed after installation, and it is beautiful and smooth. It is generally used for instruments or precision Mechanically; countersunk screws are used where the nail heads are not allowed to be exposed.

2. Hexagon socket and hexagon socket screw

The head of this type of screw can be embedded in the component, a larger torque can be applied, the connection strength is higher, and it can replace the hexagonal bolt. Commonly used in joints with compact structure and smooth appearance.

3. Cross recessed ordinary screws

It has a similar function to ordinary slotted screws and can be replaced with each other, but the cross-slotted ordinary screws have higher groove strength, are not easy to be bald, and have a more beautiful appearance. When in use, a cross-shaped screwdriver must be used for loading and unloading.

4. Eyebolts The eyebolt is a kind of hardware accessory for load-bearing during installation and transportation. When in use, the screw must be screwed to the position where the supporting surface fits tightly. No tools are allowed to be tightened, and no-load perpendicular to the plane of the lifting ring is allowed to act on it.

  1. Locking screw

The locking screw is used to fix the relative position of the machine. Screw the locking 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.

6. Self-tapping screws

When the self-tapping screw is used on the connected part, the connected part does not need to be threaded in advance. When connecting, use screws to tap the threads directly. It is often used to join thin metal plates. There are two types of tapping screws with taper end and tapping screws with flat end.

7. Self-tapping locking screws

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