RE: [CAD_CAM_EDM_DRO] Gluing aluminum

Bruce,

gluing aluminum is a technique used in the manufacture of wings for
gliders, to cite one example. However, your parts have to be CLEAN, meaning
strong solvent wash followed by an acid wash to etch the surface, followed
by energic rinsing, followed by IMMEDIATE gluing. So you see, it's not easy
but can be done.

But, as you are obviously not building an airplane, some straying off the
procedure might be acceptable. First, don't bother gluing thin parts that
are subject to some flexing. This works best with thick pieces. Second,
don't glue two materials having different coefficients of expansion. Third,
your parts have to fit closely together. Fourth, the glue works best in
shear, not in peel or in tension. You have to design your joints
accordingly.

The glue to use is obviously Epoxy. One type that would work well is
Devcon's Plastic Steel. It is a two-component paste that contains steel
particles. They strenghten the epoxy. There is also another advantage, that
is to separate the two aluminum parts by a few mils. I have read somewhere
tha the optimum thickness of epoxy for gluing metals is 6 mils. Buy a good
brand of epoxy at an industrial supply store, not at the supermarket.
Loctite and Permatex also manufacture excellent products.
Oh, and never use 5-minute epoxy for this ! You want the type that takes at
least 10-12 hours to harden.

Now, to use it, at least wash your parts very well with lacquer thinner or
equivalent to completely degrease them. Sand lightly to remove surface
oxyde. Wash again. Never touch the surfaces with your bare hands. Any trace
of oily residue will hamper adhesion. Now, mix a small batch of epoxy with a
little lacquer thinner, just enough to make it flow more easily.
Now spread a thin coat on both surfaces with a clean plastic squeegee. Then
take a stronger but soft piece of plastic and work the epoxy into the
surfaces by scrubbing it in.

After this is done, lightly scrape it off and throw it away. Don't scrape
too hard. The bare metal must not be exposed to air. Wait 15 minutes for
evaporation of all traces of solvent.
Mix a new batch, apply it, clamp your pieces firmly together while wiggling
them to exclude air and wait at least 12 hours.
They are now glued for life.

Have fun,
Guy


-----Original Message-----
From: Bruce Klawiter [mailto:bruce@...]
Sent: Friday, March 08, 2002 3:00 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Gluing aluminum


Sometime back I watched a show about building the new Maserati, Bugatti?
They built the frames out of aluminum and glued and screw the frame
together, the screws just holding things together until the glue dried. What
type of glue is this?
It seems to me is it will hold a car frame together it should be strong
enough for a metal working machine. Mite be I just have to many pie in the
sky ideas.

Bruce