Here is a simple checking way for thread ring gauges and plug gages. First, Use the ring gages to check the external threads of mating parts. Once the Go ring gage can go through the whole thread, the NOGO end can be stopped in three turns. Then we can judge the external threads are fine. Second, use the plug gauges to check the internal threads of mating parts. Once the Go plug gage can go through the whole thread, the NOGO end can be stopped in three turns. Then we can judge the internal threads are fine. Finally, we can fix the external and internal thread together, if they can be screwed well, then we can simply judge the ring gages and plug gauges are fine.

It is not permitted to fix the ring gages and plug gauges together directly, which is not correct and will hurt the gauges, in this blog, Can same size ring gage and plug gage fit together, has explained the reason in detail.

Of course, the best way for checking thread gauges is to send out to professional calibration lab to get the long form calibration certificates. They will provide accurate calibration results. But the problem is it need more time and take extra calibration costs.