Walter Dodson was saying that he was trying to figure out how to recess the
countersunk washers.  Brent says you do not need them but anyway this is how
I recessed the tinnermans I used on my cowling.  The O/D of the #8 tinnerman
is 9/16".  I marked out the hole centres but did not drill them, using a
brand new high quality Forstner wood working bit I carefully recessed the
hole.  The Forstner bit, in wood, gives a perfectly square bottom hole and
will give you the same in glass.  My tinnermans fit flush.  I am not using
any fancy fasteners, just plain old #8 S.S.Torx screws.  I cannot abide
those Phillips screws.  There must be a place in Hades for the inventor.  I
buy the best quality Phillips drivers but still no joy.  We have a screw up
here called the Robertson with a square recess in the head.  These beat
Phillips and they stay on the end of the driver when you want to poke them
in awkward places.  However you cannt always get them in good quality screws
and never in traceable form.

Ian Crowe.