Representation method for metric threads of fasteners

The representation method for metric threads is as follows:

Tooth symbol: Metric threads are generally represented by M.

Nominal diameter: Refers to the nominal major diameter of a thread.

Thread pitch: Refers to the distance between two adjacent threads, and coarse thread pitch can also be left blank (default to coarse thread if not marked).

Direction of rotation: Most commonly used threads are right-hand threads and do not need to be labeled; Left-handed threads need to be labeled with "LH", such as M12X1.5LH, which represents M12 threads and left-hand threads with a pitch of 1.5.

Thread outer diameter tolerance code: composed of numbers representing the size of the tolerance level and basic deviation letters for position, such as 6H, 6g, 6e, etc. (internal threads are represented by uppercase letters, and external threads are represented by lowercase letters)

Tolerance length: The code for the thread engagement length, generally referring to the length of the bolt.

For example, M16X1.5LH-6gX50, the meaning of this representation method is the metric thread of M16, a left-hand thread with a pitch of 1.5mm, an external thread accuracy of 6g, and a bolt with a nominal length of 50mm.