What is a limit thread gauge?

The limit thread gauge is a set of GO and NOGO. The GO can pass the thread under test smoothly, and the gauge must stop within 2 rotations (tooth) for this thread to be qualified.
Thread bolt gauge (also known as plug gauge, thread bolt gauge), thread bolt gauge is a gauge for checking female threads.
Thread ring gauge (also called ring gauge, ring tooth gauge), thread ring gauge is a gauge for checking male threads

The accuracy of ring gauges and bolt gauges must comply with "international standards" such as ISO, JIS, ANSI, DIN, BSI, etc. The accuracy test report is also attached. However, each brand has some "tolerance" in the specification. Therefore, it is recommended to use the "same brand" ring bolt gauge for testing with the corresponding manufacturer, which is less prone to tolerance disputes.

◎ Specifications
According to the requirements of different "workpiece types" and "tooth pitch", ring gauges and bolt gauges can be divided into:
M metric thread, UNC American thread coarse thread, UNF American thread fine thread, UNEF American thread extra fine thread, W inch thread, Parallel threads for PF pipes, parallel threads for NPSM American pipes, pitch thread gauges for PT British pipes, pitch thread gauges for NPT American pipes, BC bicycle etc.

Specification accuracy:
1. "ISO" metric standard: the commonly used grade of general bolt gauge is 6H, and the grade of ring tooth gauge is 6g
2. "JIS" new standard: the commonly used grade of general bolt gauge is 6H, and the grade of ring tooth gauge is 6g.
3. "JIS" old standard (divided into work and inspection): grades are divided into grades 1, 2 and 3 (commonly used grades are grade 2).
4. "ANSI" American standard: The grade classification is the same as the new JIS, but the tolerance range is different (not mixed).
American teeth: (UNC, UNF, UNEF, UNS, UN)
1. "JIS" old system standard: bolt thread gauge grades are 3B, 2B, 1B; ring thread gauge grades are 3A, 2A, 1A.
2. "ANSI" American standard: the grade is the same as the Japanese standard, but there is no difference between work and inspection, and the tolerance range is also different.

JIS is a Japanese standard. According to the purpose of use, thread gauges are divided into two types for work and inspection, while ISO standards have no such distinction.
According to the purpose of use, the Japanese JIS standards can be divided into: GP-IP (inspection regulations), GP-WP (working regulations), and GP-NP (ISO standards).

Example: outer diameter 3mm, pitch 0.5mm