Proud Liberal said:
It is a customer requirement. I have done extensive research on my own using Google to find the definitions on-line. The customer's published drafting standard doesn't cover the topic and they expect ± .005" tolerance on thread depths. I looking to head-off any problems in the future.
As the new guy here, I hesitate to change an inspection procedure that has been used for a long time. But, as our customer is constantly bringing in new inspectors, I would like to be able to quote chapter and verse of what the definition actually says. Additionally, if our methods (which is using a visual system and picking out the end of the last FULL thread by eye) perform the task, I prefer to leave the status quo alone. But if they are inadequate, I need to improve them immediately.
I also don't want to purchase a standard simply to search through it and not find the answer.
Methods of reading thread plug gages depend on the type of thread. I have a hunch from your description you are talking about a tapered dry seal pipe thread. If I am correct, your easiest source is the manufacturer of your gage. Even with all my experience on internal and external threads, I would hesitate to come and give you a tutorial.
Some manufacturers can follow the Standard for a tapered thread and come up with anything from zero-step to six-step internal and external thread gages. You ought to confer with your customer on his method and instrumentation for checking and try to replicate it as closely as possible.
When I was in the position you seem to be in, I went so far as to purchase customer's and my gages from the same manufacturer, built to the same master gage. Depending on the product and the application, this
[thread gaging] can be a zero concern or a major concern. The customer is
ALWAYS the driving force on the magnitude of the concern.
Ultimately, on some applications, even resorting to independent testing labs may not be "politically" feasible - you must reach agreement on method and instrumentation with customer to avoid a
"he said - she said" scenario.