The general sink head is used in a place where the surface is smooth and not raised after the connection is required, because the sinking 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 large.
In addition to the need to meet the locking of the installation, there is a hole in the head, the rod has holes, these holes can make the bolt vibration when not loose.
Some bolts with no thread of light rod to be fine, called the waist bolt. This bolt is advantageous to the coupling of the variable force.
Steel structure has a dedicated high-strength bolts, the head will be bigger, the size also changes.
In addition, there is special use: t-groove bolt, machine tool fixture used the most, the shape of special, the head on both sides to cut off. The anchor bolts are used for fixing the machine and the ground connection, and there are many kinds of shapes. U-shaped bolts, as described earlier. And so on。
There is a special stud for welding, a thread has no, can be welded on the part, the other side directly screw nuts.