Hexagonal bolts are hexagonal head bolts (partial threads) – class C and hexagonal head bolts (full threads) – class C. Also known as hexagonal head bolt (rough) wool hexagonal head bolt, black iron screw.
Commonly used standards can be referred to: SH3404, HG20613, HG20634 and so on.
Hexagonal bolt: A type of fastener consisting of a head and a screw (a cylinder with external threads), which needs to be matched with a nut to fasten and connect two parts with through holes.
This connection form is called bolt connection. If the nut is screwed off from the bolt, the two parts can be separated, so the bolt connection belongs to the removable connection.