What are the classifications of bolts? According to the way of connection, the points are divided into ordinary and reamed holes. According to the shape of the head: there are hexagonal heads, round heads, square heads, countersunk heads, etc. The hexagonal head is the most commonly used. Generally, the countersunk head is used where the connection is required.
The type of thread according to the thread is divided into two types: coarse teeth and fine teeth. The coarse tooth type is not displayed in the bolt symbol. Bolts are classified into 3.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, and 12.9 grades according to performance grades. Among them, grades 8.8 or higher (including grade 8.8) are made of low carbon alloy steel or medium carbon steel and heat treated (quenched). + tempering), commonly known as high-strength bolts, below 8.8 (excluding 8.8) is commonly called ordinary bolts.
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