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Reply-To: "Doug Waddingham" <DougWaddingham@worldnet.att.net>
From: "Doug Waddingham" <DougWaddingham@worldnet.att.net>
To: "Lancair List" <Lancair.list@olsusa.com>
Subject: Hole drilling
Date: Wed, 19 May 1999 17:53:27 -0600
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I'm set to drill the holes in the forward hinge canopy hinges on the LNC20.
I need to drill four 3/16 holes through 28 layers of e-glass and 1/4" of
aluminum. The plans say I need a snug fit for the AN-3 bolts. The drilling
will be done in a somewhat awkward position and I'm wondering if there is a
method I can employ that will ensure a nice round hole that goes STRAIGHT
through. A drill press is not an option. Any suggestions on how best to
accomplish this will be greatly appreciated.

Thanks

Doug


[There are several discussions in the archives about the best ways to
assure the perpendicular drilling of holes when the use of a drill press
is not an option, and in general most folks like the idea of using a 
fixture to guide the drill bit which _has_ been drilled on a drill press
to provide drill guidance.  In this instance, though, since you're drilling
two dissimilar materials it might be best if you attack the problem in
stages... If it's possible to predrill the aluminum (hinge brackets) it 
would be best to do so and manufacture your drilling jig at the same time.

I would notch a piece of hardwood to accept the leg of the "T" of the 
bracket and drill the 4 mounting holes through the AL bracket and the
hardwood at the same time.  I would use standard jobbers drills to do
this task as they will give the best results when drilling through the AL.
(Naturally I would 'sneak up' on the final #12 size by drilling the
bracket and hardwood jig in several steps, starting with 3/32" and 
working my way up to #12.)  This part of the process is done on the drill
press.

Once the AL and jig has been drilled I would spot attach it where it goes
on the mating part with thick CA and a clamp and then drill the fiberglas
using a #12 drill which has been sharpened as if for drilling plexi...
where the leading edge of the cutting surface has been made flat so the 
drill bit doesn't 'grab' the material being drilled.  I'm no machinist but 
we have many subscribers who are and would be better at describing this
sharpening method than I.  (Seems to me that it is also described in 
the assembly manual as well.  Carbide tipped masonry bits are sharpened
this way, BTW, undortunately I've never heard of a #12 masonry bit <g>.)
The holes through the hardwood block  would provide the desired guidance 
for the #12 drill bit and bolts could be inserted into each of the holes
as they are drilled to insure that nothing moves during the process.

This would be my approach, and I'm sure there are others... hopefully we'll
get some options here.  I hope this helps out.

    <Marv>   ] 




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