A hex head, round head, square head, countersunk head and so on. The hex head is the most commonly used. General countersunk head used in request connection bolt
Smooth surface after not protuberant place, because countersunk head can be twisted to the parts. Round head can also screw into the parts. Square tightening force can be some, but size large. In order to meet the needs of the lock after installation, with a hole in the head, rod department have hole, the hole can make bolt vibrated loose when not. Some bolt didn't thread of the polished rod to do fine, that wasp waist bolt. This kind of bolt to be inotropic coupling. Steel structure on the special high strength bolt, the head will do some bigger, size also has the change. In addition, there are special use: T slot bolt, machine tool fixture with the most special shape, side of head to cut off. Anchor bolt, used for machine and ground connection fixed, there are many shapes. U bolt, as aforesaid. And so on. And solder special stud, a head of a thread a head of no, can welding in the part, the other side direct screw nut.Different types used different place,
Material: usually have carbon steel,stainless steel.brass,Titanium.
Class: 3.6,4.8,5.6,6.8 ,8.8,10.9,12.9,surface,main have zinc plated.black oxide.
Bolt types: hex cap bolt, U-bolt,flange bolt.T-bolt,suquare bolt.carriage bolt,hex socket bolt.U-bolt,hang bolt,Tie wire bolt.thumb bolt. And so on.