1. According to the force mode of the connection, there are ordinary and reaming holes used. The bolts for reaming holes shall be fitted with the dimensions of the holes and used in the transverse force.
2. The head of a six-angled head, rounded, square-headed, Countersunk, the general countersunk head is used in a place where the surface is smooth and not raised, since the countersunk head can be screwed into the part. The round head can also be screwed into the part. The tightening force of the square head can be larger, but the size is very large. Six corners are the most commonly used.
In addition, in order to meet the needs of the lock after installation, there is a hole in the head, the rod has holes, these holes can be caused by the vibration of the bolt not to loose.
Some bolts without thread of light rod to do fine, called the waist bolts. This kind of bolt is advantageous to the connection of the variable force.
There is a special high-strength bolt on the steel structure. The head will be bigger. The size also changes.
In addition there are special uses: T-groove bolts, machine tool fixture on the most, the shape of the special, the head on both sides to cut off. Anchor bolts for machine and ground connection fixed, there are many kinds of shapes, U-shaped bolts, such as the foregoing.
There is also a special stud for welding, a thread end is not, can be welded on the part, the other side directly screw the nut.