FTM 187: What happens when ring gauges don’t agree

FTM 187: What happens when ring gauges don't agree

This edition of the Fastener Training Minute with Carmen Vertullo was originally published April, 18th, 2023 as “We have a fastener, our ring gauge says it is OK, the customer’s ring gauge says it doesn’t conform. What do we do?” during episode 187 of Fully Threaded Radio.

Well hi everybody, this is Carmen Vertullo with the Fastener Training Minute coming to you from the Fastener Training Institute and the Carver Fact Center in El Cajon California.

Today’s topic comes from a former student who had a non-conformance problem generated by their customer, because some threaded Eye-Bolts that they sent would not take the Go-Gauge on the threads. So they called me up and said: we don’t understand it, the customer complains it won’t take their go-gauge but it takes our go-gauge. What the Hell? So when I come back, we’ll talk about how we can resolve the issue regarding my gauge works and yours doesn’t on externally threaded fasteners.

Well hi everybody, welcome back to the Fastener Training Minute, and today’s episode regarding one gauge works and the other does not. This is a relatively easy problem to solve because the standards that govern our inch threads ASME B1.1, ASME B1.2 and ASME B1.3 deal with this problem very well. In ASME B1.2, which governs how we use our gauges, it’s very clearly stated that if any particular acceptable gauge finds the thread characteristic acceptable, then it is deemed acceptable. Now it goes without saying even though it’s not written in the standard but it is implicit or implied, that even if another acceptable gauge finds the part not in conformance, it is deemed acceptable. So it only takes one acceptable gauge to make the part conforming. If  another one finds it not conforming, too bad.


Now when this happens, the chances are that the part is pretty close to the edge, and if one Go ring-gauge finds the part in conformance: that is it Goes, and the other one does not Go, you might want to check calibration. Ring gauges are very delicate. If, for example, you drop one on the floor, it could very easily run that gauge out of tolerance. And then it wouldn’t work. Or you could find another method to inspect the threads, such as variables gauging, which is not a requirement but a really cool way to inspect external threads. And maybe that gauge would find it acceptable. Regardless of what that gauge finds, it should find that the part is very close to the edge when one ring gauge takes it and another doesn’t. Now on the upside, the way threads and fasteners are designed is that threads that are very close to the edge (even over) will still work. Okay it is not a problem. And at the end of the day one of the best solutions might be to say to the customer: “Hey what are you going to do with this thread are you going to screw a nut on to it, or you going to screw it into a tapped hole. Let’s  see if it’ll Go”.

And if it Goes then it could be the end of the problem, and you just move on to something that actually requires a solution. Well there are lots of other things that can cause our external threads to be not accepted by the same user in on their next Fastener Training Minute we will discuss some of those.

This has been the Fastener Training Minute thanks for listening

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