Close tolerance bolt

Just trying to confirm that an AN173-4a close tolerance bolt is basically the same as an AN3-4A just manufactured to closer tolerances.

It pretty much is but might be slightly thicker. The strength is the same. I just checked the specifications.

AN3 diameter is .186 to .189 inches.

AN173 diameter is .1889 to .1894 inches.

Dave

Yes...but.

They are machined after plating for close tolerance fit, which trims the plating to a very consistent diameter. Most any bolt can achieve a somewhat close tolerance fit if the diameter of the fastener is matched to a correct drill/reamer size. Not needed or practical in most RV joint design. NAS bolts have a closer overall fit and uniformity, and there are others I work with that are extremely close, then you can get into transitional fit and interference fit when the magic really happens. No need in the RV, even though I did it on mine some places, just because.

No need?

Close tolerance bolts are specified for the spar attachment on the -10...

Close tolerance bolts also have a shorter thread length on the same overall length bolt. A plus in some instances where the full bolt thickness is longer.

Clarifying the "no need" in my post..

Sorry all, my comment of the "no need" in an RV was specifically for the transition fit and interference fit I mentioned..yes, RV's have close tolerance in several places, mostly spar carry through and landing gear. My rule of thumb is close tolerance fit in permanently attached structure. Fatigue starts when there is movement within the joint. I built my RV-4 with Hiloks (transition fit) in some areas where plans called for AN bolts that would normally be used.A Hilok is installed in a hole slightly smaller than the diameter of the fastener..very tight fit.