Date: Thu, 10 Feb 2000 09:42:50 -0500
From: Lynda Frantz <LFrantz@compuserve.com>
Subject: Metal receptacle for countersunk machine screws
Sender: Lynda Frantz <LFrantz@compuserve.com>
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>>>>I seem to recall that Jim Frantz mentioned that he installed the
countersunk
stainless washers by making a recess the diameter of the washer into the
cowl (I would like to know how), and then glassing the washer in place
to seal it in and provide a flush finish with a metal seat for the screw.
Clever idea, and may be what you saw.<<<<

Correct.  I made a special countersink cutting tool that fit in my
microstop countersink that allowed the nickle plated Tinnerman to sit flush
with the surface.  The Tinnermans are only .018" thich so the countersink
hardly cut into the composite part at all.  The tinnerman was bonded to the
composite part using structural adhesive and one bid applied over the
tinnerman is recommended.

The above procedure is additional work but those elevator, and engine cowl
attach points, and etc.  will last a long time with no pull through or
paint cracking around the machine screws.

The countersink cutting tool I used is similar to a countersink cutter 
with pilot except it is a face cutter rather than the common 100 degree
cutter.  I  machined mine out of cutting steel which was easy to do with a
laythe and then tempered  it.  Your local tool maker will do this for under
$100.  Or you might be able to modify a standard 100 degree cutter by
de-tempering it, modifying the cutting face and then re-tempering it
although I never thied this idea.  The diameter of the cutter has to match
the diametr of the tinnerman (1/2") and you should use a tinnerman intended
for one size smaller machine screw.

Some folks just pot the Tinnerman on top of the composite and then use
fillers and one bid over the top,  but this requires more body work and
fill to get that show quality paint job.  

Jim Frantz 
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LML website:   http://www.olsusa.com/Users/Mkaye/maillist.html
Builders' Bookstore:   http://www.buildersbooks.com/lancair

Please send your photos and drawings to marvkaye@olsusa.com.
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