You require precision tools in industries every time. Every item of machinery, right from the humble screw to the heaviest machinery would require quality checks to work well. You can never underestimate the importance of the smallest piece of machinery as well. You would never imagine that the malfunctioning of a single screw could bring down an airplane from the sky to the ground within minutes. This brings us to the aspect of conducting checks on the machinery parts before dispatching them. You would be surprised that the industry demands quality checks on every single screw or nut that comes out of the industries. The equipment they use to check the tolerance levels of the screws and other threaded machinery are the thread gauges. Depending on the location of the thread, you use the different kinds of thread gauges such as UNEF thread gages.
The screw might be the most humble industrial tool. However, history has shown it to be the most important. The industry has to ensure that every screw that leaves the industry and enters into the market should pass the tolerance tests comfortably. This would not be an arduous test at all. They have to pass a simple Go and No-Go test. The UNEF thread gauges help in conducting these tests. Every screw has to undergo this test. The test is such that the screw should easily pass through the Go kind of thread ring gauge while it should not do so with the No Go thread ring gauge. If they manage to do so, the industry can pass the screw as fit for the market. Otherwise, they require improvement in the design.
Similarly, the implements having the threaded portion inside their body would not be in a position to use the thread ring gauge. You need specific instruments such as the thread plug gauges for checking the tolerance levels. This would be a simple implement having the Go and the No Go options at its two ends. In this case, instead of the implement going into the tool, the tool has to go into the implement. The Go side of the plug should enter the nut or the pipe easily. At the same time, the No Go side should not penetrate the nut or the pipe. In such an eventuality, the implement can pass the muster.
The industries in US and Canada follow the UN measurement scales. Some of the threads in use in the industry are coarse threads whereas some are fine threads. You need UNF thread gages to measure tolerance levels of fine threads. The UNEF thread gauges come into the picture when you have extra fine threads. The best kind of test is always the GO and NOGO test. Threads that pass this test are certified fit by the industry.
This might seem to be a trivial test. However, the industry requires the same. You should never underestimate the quality control measures for confirming the tolerance levels of these simple tools. They are simple but very important.