What are the main classifications of screws

Update:10 Aug 2020
Summary:

Screw, which is also called fastener or standard part; […]

Screw, which is also called fastener or standard part; the English name of screw is screw, which is basically used in the place with prefabricated thread; the English name of bolt is bolt, which is used together with nut, and the tool is generally wrench.

The main classification of screws includes ordinary screws, self tapping screws and expansion screws.

Cap screw used to be limited to full tooth fasteners, but this is not the standard use now.

Generally speaking, machine screw is a screw with a diameter less than & frac14; inch (4 ා ~ 12 ා), which is usually full teeth and rotated by a driver, such as slotting, cross or hexagon.

As the name implies, Hex Cap Screw and hex bolt are hexagon type external thread fasteners, which are designed to be turned by wrench. According to ASME b18.2.1, the tolerance of head height and rod length of Hex Cap screw is smaller than that of general hex bolt. Therefore, ASME b18.2.1 hex head screw is suitable for installation where all hexagon bolts can be used, and where large hexagon bolts are too large to be used.

Socket cap screw, also known as socket screw or Allen bolt, is a screw with a hexagonal hole in the head. It can only be tightened or loosened after it is inserted into the hole with hex key, Allen screw or Allen key. The cylindrical head screw is the most commonly used hexagon socket head screw. The head diameter is about 1.5 times of the main thread diameter (1960 series). Other head types include the bottom head cap screw which makes the surface beautiful and the countersunk head cap screw suitable for the conical screw hole. The countersunk design allows the screw head to rotate without being exposed on the surface of the fixed object, so it is often used in places where the surface is small and the traditional spanner is inconvenient to use.