Limit gauges for screw threads are graded in the same manner as screws. Screw threads are inspected according to two limits defined by GO and NO GO gauges. The Previous JIS gauge system provides two categories of NO GO gauges depending on the purpose of usage: machining and inspection. This classification is not used in the ISO system. Screw threads pass the inspection if the GO gauge, when screwed by hand without using excess force on the thread under test for the specified engagement length, goes over the entire thread length, and if the NO GO gauge, when screwed by hand without using excess force, enter on both sides by not more than two turns of thread (not more than three turns of thread in ANSI).
OSG
Standard Thread Gauge (SG)
A gauge created in accordance with the basic profile of screws and standard dimensions. A plug gauge and ring gauge that fits one another perfectly comprises a single set. Can be used as a standard gauge (master gauge) and can also conduct inspection by directly using it on a male or female thread.
