Self drilling screws are usually classified as self-tapping screws, which are also self-tapping thread. The tail is different from ordinary self-tapping screws. It is a drill bit rather than a pointed tail.

A self-tapping screw is a screw with a drill bit, and they are composed of three parts: the head, the shank and the end of the shank. At present, most of the self-tapping screws on the market are made of carbon steel and stainless steel. Both carbon steel and stainless steel self tapping screws need to be heat treated, so that the self tapping screw can reach the standard mechanical properties. The surface hardness of self tapping screws is high, and the internal toughness is good, so self-tapping screws can drill into relatively hard places.

There are many surface treatments for wood screws, electro-galvanizing/zinc plating is the most widely used method, because zinc is easy to be plated and price is relatively cheap compared to other metal materials.

The main function of wood screws is to fasten a metal (or non-metallic) part with a through hole to a wooden component, so there is no high requirement for its material. Usually, the most common types of wood screws are mainly two types.

Hexagon head wood screws also known as wood screws, which are similar to machine screws. But the threads on the screws are special threads for wood screws, which can be directly screwed into wooden components (or parts), used to screw a metal (or non- metal) parts are fastened together with a wooden member. This connection is also detachable connection.

Pan head screws include one slot and cross slot for choice. If using electric screwdriver for installation, the cross slot is generally selected. The materials of pan head screws are mostly iron and stainless steel, iron are low carbon, medium and high carbon steel, and the materials of stainless steel screws are stainless steel 201, stainless steel 304 and stainless steel 316.

Countersunk head screw, also known as flat machine screw, its head is a 90-degree cone, similar to common wood screws. On the surface of the mounting hole on the connector, a 90-degree conical socket is machined, and head of the countersunk head screw is in the socket and is flush with the surface of the connector.

Machine screws, also known as machine screws, are also one of the most commonly used fasteners. Machine screws are usually used alone (sometimes with washers), and generally play a fastening or tightening role.

Flange nuts can be divided into two categories according to the material. The first is ordinary carbon structural steel, which is what we usually call carbon steel; the second is stainless steel. Carbon steel is divided into Q195, 08AL and alloy steel according to the carbon content and strength of the steel. Stainless steel is divided into 304, 321, 304L, 316, 316L, 317, 317L, 310S and so on.

The surface treatment of DIN6923 flange nuts is generally divided into two types: yellow zinc and zinc plated, they are cold-galvanized. For hot dip galvanizing, hex flange nut is inappropriate. This is because the residual zinc sticking to the thread after hot-dip galvanizing is not easy to remove, and the thickness of the zinc layer is uneven, which affects the fit of the parts.

A flange nut is a nut that has a wide flange at one end. This helps to distribute the pressure of the nut over the part being secured, reducing the damage of the part and making it less likely to loosen as a result of an uneven fastening surface.

According to provisions of the national standard GB/T 3098.2-2015 "Mechanical Properties of Fasteners Nuts", bolts made of carbon steel and alloy steel have 7 types of mechanical properties under the condition of environmental dimension of 10℃～35℃. They are 04, 05, 5, 6, 8, 10, 12 respectively.