M2 carbon steel hardened thin head black zinc plated blue patch screw

Industry knowledge：

How to distinguish whether stainless steel screws are qualified?

The specification range of precision small screw refers to the screw whose outer diameter of thread is less than or equal to 3mm. Because of its small volume and high manufacturing requirements, it is called precision small screw. There are three head types in the scope of national standard, namely round head cross drive, countersunk head cross drive and semi countersunk head cross drive. However, there are some other head types in actual production, such as slotted drive, hexagonal slot drive, in addition, there are some other uncommon drives, such as Y-shaped, triangular slot drive, square slot drive, etc.