I. Classification of Screws
According to the assembly method, screws can be classified into mechanism (mechanical) screws, self-tapping screws and self-drilling screws.
Mechanical (machine) screws: During assembly, holes need to be drilled and tapped on the assembly parts first. The internal thread specifications should be consistent with the external thread specifications. Use a smaller torque for assembly.
Self-tapping screws: During assembly, drill holes on the assembly parts first. No need to countersink. Use a relatively large torque for assembly.
Self-drilling screws: Used directly on assembly parts, they can be screwed into the holes and countersunk at one operation, such as wood screws, tail screws, etc.
Other common types of screws include set screws, non-detachable screws, locating (locking head) screws, and ring screws, etc.
II. Key Parameters of Screws:
Thread The thread consists of five elements: tooth profile, nominal diameter, number of threads, pitch (lead), and helix direction. When using internal and external threads in pairs, the above elements must be consistent.