Posted for "Gary Rodgers" <gcrodgers@sympatico.ca>:

You may have seen my post where I mentioned that I use a methyl methacrylate
adhesive for bonding aluminum/fiberglass and I mentioned that I also use it
for bonding nut plates.  This is my procedure.

I usually make up a bunch ahead of time in the size ranges that I use.
  1.. place the nut plates in a solvent.  I use MC
  2.. while the plates are in the solvent I prepare several strips of ~2-3
bid fiberglass or carbon fiber (that have been previously made or cut-off
strips from some other fabrication) by cleaning and sanding the surface.
  3.. take a nut plate from the solvent and using ~220 wet/dry sand paper I
clean the majority surface of the nut plate until you see metal and any
coating is removed.
  4.. take a wooden stir stick reduced in size so that the tip will go into
the thread area and apply petroleum jelly (Vaseline).  I usually fill the
hole being careful not to let it get on an area that I want to bond.
  5.. apply a small amount of adhesive to the bottom of the nut plate and
position on the fiber glass, then run a bead of adhesive around the nut
plate and with a wooden stir stick cover the nut plate wings and up the
threaded shoulder.
  6.. allow the adhesive to cure.  The type I use will allow me to handle it
in ~ 10 minutes.  I end up with fiberglass/carbon fiber strips of nut plates
  7.. cut off nut plates as needed, trimming to leave ~ 1/4" perimeter on
the sides of the nut plates
  8.. using a drill that is smaller in dia (will not damage threads) than
the nut plate thread, I drill down through the thread area and through the
fiber glass.
  9.. using a drill bit that is several times larger than the thread size,
and turning the nut plate over, I use the smaller pilot hole that was
drilled from the front/nut plate side as a locater and open up the hole.  If
you look at a nut plate you will see that the threads do not start at the
bottom so there is no danger of damaging threads; especially if you remember
to use the 'larger than thread size' drill bit.
  10.. often you can use the actual device that needs the nut plates
installation as the holding method when you bond it in place.  Often I have
been able to bond the nut plate directly to whatever I was working on
without the fiber glass plate if it is easily accessible at the time of
construction.  Just make sure that you apply petroleum jelly to the threads
of the bolt/screw that you are using.  Just prepare the surface and as
prepared to be bonded to the pads.
Gary R