Every one has their procedure on drilling holes for a AN3 Bolt. Here is what I do but first a note on standard bolt and drill sizes.
#13 - 0.185 AN3 - 0.187 3/16 - 0.1875 #12 - 0.189
These sizes are orders from smallest to largest. Most of the logs I look at start with a #30 and then enlarge with a #12. I found this makes a crappy hole that is oversized. The #12 wants to chatter before it takes.
I start with a #30 like every one else but then I use my special drill bit. It’s a 2 stage bit. The end is 0.148 and the rest is 0.187 The end nipple tracks in the center of the #30 very well. And the quality of the hole is very nice. I got this bit from Boeing surplus.
An alternative to the special drill bit would be to use a #13.
Then I use 3/16 reamer to get it perfect to fit the AN3 nice and tight. If you don’t have a 3/16 reamer then how about using a 3/16 bit.
I really don’t get how people use a #12 as the last dill bit for a AN3? Lots of slop and poor quality hole. Just sayin.
