Screw and bolt head type and characteristics

Update:18-09-2020
Summary:

The head shape of bolts and screws can be divided into […]

The head shape of bolts and screws can be divided into several categories
The head shape of bolts and screws can be divided into 6 categories: hexagon head, double hexagon head, spline head, pan head, countersunk head and other head shapes. Except for the countersunk head, they are all convex heads. The tensile strength of the raised head bolt mainly depends on the strength of the thread, and the strength of the countersunk head bolt mainly depends on the strength of the head.
Features of hexagon head bolts
Hexagon head bolts and cylinder head bolts are often made with lock thread holes. After the bolts are tightened, the metal wire is passed through the bolt lock hole, and a group of bolts are connected in series to restrain each other and play a role in preventing loosening together. In addition, the lock wire hole can also be used for sealing to prevent random disassembly.
Features of countersunk screws
The countersunk head can be divided into (flat) countersunk head and half countersunk head. The cone angle of the countersunk head generally has 3 types of countersunk head: 900, 1000 and 1200. In the Russian standard system, 900 and 1200 countersunk heads are used. The 1200 countersunk head is mainly used for thin-walled structures (such as thin skins), but because the thickness of the head is thin, the depth of the screwing groove is not easy to control, the groove is too shallow, the screwing performance is too poor, and it is easy to "slip when installing and removing bolts." "; The groove is too deep, it will weaken the nail head strength, easy to turn around. In the ISO/TC2 standard system, there are only 900 countersunk heads, while in the ISO/TC20/SC4 standard system, there are only 1000 countersunk heads and 1000 small countersunk heads. Small countersunk head refers to the type with reduced head height. It is used for thin-walled structures of aerospace vehicles. Due to the characteristics of countersunk bolt structure, the strength of the head is generally lower than the strength of the screw or thread. The countersunk bolt undergoes tensile failure During the test, the bolt head is always destroyed first.

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