Cylindrical head hexagon screws, also referred to as hexagon bolts, cup head screws, hexagon screws, its name is not the same

S.W. standard Whiworth coarse series general purpose cylinder thread,S.F. standard Whiworth fine series general purpose cylinder thread

current national standards1237-2000 GB/T fastening part marking method A fastening3098.2-2000 GB/T fastening mechanical properties of the nut

Countersunk head screw is also called countersunk head screw, also known as flat machine screw, is a kind of building parts. The head is a 90-degree cone, similar to common wood screws. The head has a tool tightening groove, including a shape, a cross, an inner hexagon, a quincunx, a pentagon, etc.