Rivet Consistency

This week I was able to complete the Horizontal Stabilizer, so all that's left for the tailcone/empennage kit is the elevator. The delivery of the Fuselage is going to be delayed by about a month (hopefully arrive sometime in December), so I've been going over each section identifying problems and looking at what I should improve upon moving forward. One thing that I have gotten a lot of practice with the tailcone and H-stab is riveting (a lot more practice still to come ). Throughout the first sections I have been using a rivet gauge to check rivets and would aim to have the rivet just barely fit in the hole and not be able to pass under the lip. I did this based off advice from many builders and the instructions from the manufacturer of the gauge "the gauge measures the minimum acceptable height and minimum acceptable diameter". Out of curiosity I went ahead and measured the depth of the lip and found that it was not the minimum 0.038", but that is was about 0.053". Am I missing something here? I went ahead and measured the depths of the other gauges in the set and found that they were also near the higher end of the milspec standard. Throughout the build I have made only a few modifications that I have seen other builders do with rivet sizes (but the vast majority are the Van's recommendations). I measured the diameter of the hole on the gauge and it was the appropriate 0.140". Given that I ensure that the rivets just fit over the gauge with little/no movement (I've started eyeing each rivet and checking with gauge every 10 or so rivets to ensure I'm calibrated), the rivets are the correct 1.5 X diameter, but the rivet height is confusing me. I've attached some pictures of rivets throughout the project.

https://photos.app.goo.gl/ucwRxRJDpfrZ8kjF6
https://photos.app.goo.gl/dR5snPRExTCi5YT27
https://photos.app.goo.gl/xgAwgdoV2BvxY53V8

I know that the rivets are properly set but the gauge is really confusing me. Maybe I'm just overthinking this, but based off the fact that I am following the rivet callouts and the gauge is just catching on the rivets, what is the difference between this gauge and the appropriate 0.038" gauge? The main thing I've been trying to ensure is consistency during the build and I feel as though I've done a pretty good job of it so far, but this is really throwing me for a loop.

They look fantastic.
Just use the rivet called out and your 1.5 diameter gauge.
After a while, If a rivet is Obviously too short, you’ll know it and just move up a length.
I’ve hardly ever used the minimum height side of the gauge.

Wrap some duct tape around your bucking bar and you won’t scuff up the ribs.

Looks good

All rivets look nice to me.

Remember the rivet gauge should not fit over rivet.

The hole ensures it’s been driven enough - doesn’t fit
The flat gap on other side ensures hasn’t been driven too much - doesn’t fit

I use this exact gauge on my last video.

FYI your HS looks really good

Don’t be afraid to move up 1/2 rivet length. Some extra rivets of varying lengths will make your life easier

I wouldn't sweat it too much..

(from page 5-04 in Van's build manual for RV-14)
"Poorly set and cracked rivet heads were tested in tension to determine how well formed a head has to be in order to develop full strength. The tensile strengths of all the rivets were within five percent of the strongest. The test indicated that minor deviations from the theoretically desired shape of head are not cause for concern or replacement. The second rivet that is driven in any one hole [is] likely to be more defective than the first because the hole is enlarged and [the] rivet will be more likely to buckle......"

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Some interesting results from testing riveted joints to failure in this link:

https://glasair-owners.com/resources/strength-of-riveted-joints/

The tests seem to indicate that only the grossly under-driven rivets cause significantly weaker joints

Make your own gauge like I did:

I used .040 aluminum from and drilled a 1/8" hole in it. It's convenient to put a small notch in the end of the gauge so that you can surround the rivet head, but not necessary. No need to make the notch width any particular width since there's no max diameter requirement.

If the rivet isn't at least as high as the gauge, it's too low. And if the rivet fits in the hole, it's not fat enough. Easy, simple, and straightforward.

Dave