Spline Gages ???? What?

We have a few spline gages here and we have the manufacturer certify them. We don't check them here.

The issue is that from PPAP to now the go gage has stopped fitting into the parts. So the QM is saying they are made wrong. And I don't have the knowledge to say one way or another. Comparing the manufacturer print to the customer print tells me nothing.

When we had these made the guy (here at my job) that ordered them sent the gage manufacturer the part print and said "You are the experts. Send us a gage for this." Now I'm left to figure out if they are in-fact experts and made it correctly. So I have to prove that they are good and to spec... and the QM has no grounds that they are bad or out of spec other than they dont fit current production.

My company is a precision gear/spline manufacturer

Our customers will state an AGMA or ISO spec that the spline shall conform to. We copy & paste that requirement into PO.

We then purchase a gage from our 17025 Accredited facility & they send along with it a c-of-c that says it conforms to the spec on our PO.

We WILL NOT (nor DO WE WANT) to be in the business of telling a gage manufacturer how to make a gage.

If gages worked and all of a sudden they're binding up, it is now time for re-certification. Gages will wear quickly due to the types of materials being used (especially ones with a tight fit)

First- essentially you are going off of the assumption that it is correct because the P.O. stated the print spec and applicable standard and the manufacturer provided a cert of calibration saying it does.

How do I convince others that is enough? Also, I have a hard time fully swallowing that myself. I don't want to tell them how to make the gage. I just want to confirm that we are checking our parts at the proper limits. Ya know?

Second- The parts have changed. 100%. You would think that would be enough to convince them. We have a 3 pin method to check the parts and it shows them smaller than before. However, we also have a press fit shaft that we use on a force tester. This shaft is labeled "max" from the customer stating its the max size of the shafts they use. It slides right through. But our go gage stops about halfway through and requires some force to push it the rest of the way. So they assume that means the go gage is wrong.... I tried to explain that they are two different sizes and geometrically different however.... no dice.

First: I am not going off of an assumption. I am going off of a certificate of conformance from an accredited facility. We do $30m+ yearly on these products & they're all critical safety components for aircraft & defense products that go to top tier customers. Drop the nerdrage Cheesey. The data on my PO is a direct copy & paste from my customer's technical specs.
With all due respect, convincing your clearly undereducated co-workers is not my concern.

Second: I believe you that the parts have changed. Do you have a way to prove it? Doesn't sound like it. If you want o make splines...you need to figure out what spec they need to be good to & then get appropriate gaging that is made out of the appropriate material to account for the non-avoidable wear that will occur when material rubs together.

The things your struggling with are why companies like mine specialize in this stuff. If you change your energy I will help you further. Otherwise you can go p!ss up a rope dude.

Sorry DAN_M I didn't intend to come off as an ***. I am simply trying to grasp the process here and it seems I oversimplified. I am simply ignorant when it comes to splines.

To clarify.... You send your customer specs (like the table I posted above, but also with the correct standard identified) to the accredited lab. They send you a Certificate of conformance. Justifiably this is enough to certify the gage is made correctly.

What do you do when the specs of a gage are questioned? Have you been asked "How do we know the manufacturer made it correctly?" What would your response be to them at that point.

And I agree with you... my coworkers and I are undereducated and probably don't deserve convincing, but I would like to understand. We have more splines coming down the pipeline and I would like to have some ground to stand on when I get push back from the QM and Engineers.

About the parts changing. I do have ways to prove they have changed. We retain all PPAP parts, and force test data from each run. I have documented the trends of them changing. But our quality techs have changed their way of inspecting them over time. We used to put the go gage in from the top and push through the bottom. When the go gage stopped fitting they changed the process to be inserted from the bottom. We have also changed the way we do our force test. So multiple changes on their end is making it difficult to convince them. Even though I have PPAP samples, PPAP Data, and comparison parts from multiple dates when checked the way we checked them at PPAP shows an obvious change.

However the QM has convinced everyone that its the go/nogo gage and not the spline as much. And they tasked me with confirming that it was made correctly to check our parts. And with my limited knowledge all i can say is "We gave them the specs and standard and they sent us a certificate of calibration so from my understanding its correct." which i'm sure they will want more than that.

My whole point here is when I get a plug gage made for a hole. I can take the print and calculate the size of the plug gage with 100% confidence in my results. Is this possible with splines or am I looking for an answer that is better covered by telling them to call the manufacturer for their answers?

Unless you have a Quindos CMM, a PC DMIS CMM with Gear Module (which is PC DMIS with Quindos running under the hood), a Gleason CMM, or an M&M CMM... AND...the equipment itself is certified to the accreditation level of a 17025 facility......you do not have the ability to measure your spline gage & prove it is "good". All you have is your cert.

Splines are advanced geometry that require special certification for a reason.

Thanks DAN_M for the help.