Author: ellis.h.mcgaughy-1@... Time: Mon Aug 6, 2001 6:52 am PDT Link
More info.
First, thanks to all who sent advice. There are a couple of
suggestions I intend to try.
But, let me tell you what I found so far!
I carefully drilled some holes in 1/8" aircraft aluminum. Well
lubricated, in a drill press. All holes appear perfectly round.
Holes were drilled with 2 different #12 bits (came in the same
package from Avery) and a 3/16" drill bit.
After drilling, I took 5 different AN3 bolts to see if any / all
would fit in the holes.
Results.
One of the #12 bits drilled holes smaller than the 3/16" bit. And
the other #12 bit drilled a hole larger than the 3/16" bit. There is
obviously a difference in the two #12's. The bit that was drilling
the smaller hole was the one I had been using and could not
understand why none of the AN3 bolts would fit.
I am mic'ing the bits today and will publish the results. I called
Avery .... they are great folks ... they said they have occasionally
seen this problem. I ordered 2 more #12 drills and a 3/16" reamer.
They gave me one of the drills for free (to replace the small one I
had.)
I may invest in more reamers for AN4 and AN5 size holes. This ordeal
has been very frustrating for me. When a bit is stamped #12, you
expect it to be .1890 inches. Maybe I need to buy my own micrometer
too (or maybe a simple drill gauge.)
Guess we don't live in a perfect world. Oh my gosh, I wonder if all
my work doesn't have to be perfect after all?