ToadMan8

Member
If I've learned one thing watching high school refs attempt to work NFL games, it's that having hard-and-fast rules would be better than running to the sidelines before making every decision.

One such call that has been bugging me is how large a #40 needs to get before it's too big for an AN3 rivet. The answer I've received from Van's builder assistance and experienced builders is always "if it's too big, use a NAS1097 'oops' rivet...", which begs the question "what is too big?!"

I believe I have found an (the?) "official" answer from an engineering perspective, and I'm looking for validation from you guys. MIL-R-47196A(MI) has a table (TABLE 1) that shows the "Hole Diameter Limits".

This table indicates that 3/32 rivets (AN3's) can be properly used in a hole as large as .103". This means that an AN3 should certainly NOT be used in a hole that will accept a 7/64" (.1093") drill bit. I assume most people don't have #38 and #37 drills laying around, but to be the most precise, if the hole will NOT accept a #37 drill, you should be OK to drive the original rivet. Otherwise, drill #30 and use the NAS1097.

My only bit of doubt in this is that the table is titled "... Standard Rivets". I don't know if that term means that it only applies to 470s and there is a different term that means 426s, or if "Standard Rivets" include all solid aluminum rivets.

Did I get this right??
 
Only problem with this approach is that the most common problem is that the oversize hole is not round, due to being off center when drilling out a rivet. The elongated hole will not accept the #37 bit but may be too long in the narrow direction.
 
Pragmatic approach

For a lightly loaded rivet in a line of fasteners, as long as you can get the rivet to swell enough to fill the hole, go for it. There are also NAS1241 and 1242 rivets. Drill #27 for 1/8" oversize. Genuine has some of this stuff, don't know if they have first oversize #3.
For a larger fastener that's more critically loaded, stick close to the standard you referenced.