Correct rivet length

[DesertBearhawk]

Guys, riveting on my spar. Where you have 4 cap strips the total thickness is .532. As I am using a #5 rivet ( 5/32 or .156) the total length of the rivet should be material thickness + 1.5D or .532 + .234 which is .766. Convert that to 16's and you get 12.256 ( .766 x 16) which is a #12+ rivet. If you do the math on .256 of a 16th you get .0156 or 1/64 (.0625/4=.0156). After bucking the #12 rivet I get a shop head that is .234 or 7.5 32nds which is 1.5D and a height of .078 or 2.5 32nds which is 1/2D both of which is the nominal dimensions. I tried to set a #13 under the same scenario and had problems with the shop heads baby-shooing and cracking. This was using a C-frame to drive them so everything was square. My question to the crew is this, is the 1/64th of an inch of length on the un-bucked rivet a no-go issue if the final shop head is the proper width and height? BTW, I dialed up .0156 on my micrometer and it ain't much, well within visual error range. Additionally, I have multiple aircraft I can eyeball at work from G550's to Cessna 150's and I have to say the quality of the rivets I'm driving are outstanding in comparison, guess 50 million don't buy what it used to! So, what say you guys?

[bestbearhawk1231]

If the shop head is proper dimensions with the #12 and the #13 is giving issues, I would probably go with the #12. Maybe I am confused or read the question wrong but if you are pulling out a micrometer to check your shop heads it may be a little extreme. I generally use the go- no go gauge to determine the shop head. After seeing what Falcon and Leer allowed in their jets, I would say that a go- no go gauge is plenty accurate.

[DesertBearhawk]

Don't get me wrong, I'm not checking each rivet with micrometer. I am just doing the math....I measured the shop heads tonight and I am 4-8 thousands over nominal dimensions so I believe I am good...

[bestbearhawk1231]

If you like i can check my reference material tomarrow at the shop and let you know what the tolerance is. I normally do the math or use a tail length gauge to get close then let the rivet tell me what they want to do when I test the length on scrap metal and use my shop head gauge to check the shop heads.

[X'N]

I agree with Bestbearhawk with using a go/no go. In A&P school the instructor had us make our own gauges out of steel pallet strapping strips. Nothing more than a hole in the end of a 3" long strip that was sized just under what 1.5 d shoudl be it should not slip all the way over the shop head... The other end had a notch made with a file that had the 1/2 d dimension. I'll see if I can find them and snap a picture.

On a side note if you have an Iphone or ipad get the Rivet sizer app. Just a quicker way to figure out your rivet length. As for the length don't sweat the petty suff, pet the swetty suff

[Jflyer]

There's an APP for that !

And its awesome. Thanks Dan.

[Erbman]

I seem to remember needing an AN5-13 rivet for that application, and all that was available was AN5-12 and AN5-14. I ended up cutting longer rivets to the -13 length.