1. According to the force mode of the connection, there are ordinary and reamed holes. The bolts used for reaming holes should be matched with the size of the hole and used when subjected to lateral forces.
2. According to the shape of the head, there are hexagonal heads, round heads, square heads, countersunk heads, etc.Generally, countersunk heads are used in places where the surface is required to be smooth and no protrusions after the connection, because the countersunk head can be screwed into the part. The head can also be screwed into the part. The tightening force of the square head can be larger, but the size is large. The hexagonal head is the most commonly used.
In addition, in order to meet the need of locking after installation, there are holes on the head and holes on the rod. These holes can prevent the bolt from loosening when subjected to vibration.Some bolts have no threaded polished rods to be thin, called thin waist bolts. This kind of bolt is conducive to the connection of variable forces.
There are special high-strength bolts on the steel structure. The head will be larger. The size will also change.In addition, there are special uses: T-slot bolts, the most used on machine tool fixtures, special shapes, and both sides of the head should be cut off. Anchor bolts are used to connect and fix the machine and the ground. There are many shapes, U-shaped bolts , As mentioned above and so on.
There are also special studs for welding. One end has a thread and the other is not. It can be welded to the part, and the nut is directly screwed on the other side.