screws

a) Machine screws: divided into many varieties due to different head shape and groove shape. The head type has a cylindrical head, a pan head, a countersunk head and a semi-recessed head. The head groove shape is generally a slotted (slotted groove), a cross slot and a hexagonal slot. When the Phillips screw is screwed, the neutrality is good, the strength of the head is larger than that of the slot, and it is not easy to be bald. It is generally used in mass production. Hexagon socket head cap screws and hexagon socket type screws can apply a large tightening torque. The connection strength is high and the head can be buried in the body for a compact and smooth joint. See GB65, GB67~69 and GB818~820;