Alt-BEAM Archive

Message #04548



To: beam@sgiblab.sgi.com
From: Bruce Robinson Bruce_Robinson@bc.sympatico.ca
Date: Wed, 16 Jun 1999 11:57:37 -0700
Subject: [alt-beam] Re: glue for metals...


"G.R.Reddy" wrote:
>
> I am having problems sticking two 1mm thick sheets of aluminum. I tried
> araldite and other general purpose epoxy glues, but its not strong
> enough. I would really appreciate if some one can suggest me some sure
> shot glue to stick aluminium.

Aluminum just doesn't seem to want to "stick", does it. Actually, it's
possible to do all those things you "can't do" with aluminum -- solder
it, weld it, glue it. The catch is, you need lots of special knowledge,
skill, and experience. Even professional welders hate the stuff.

As for gluing -- some epoxies work, although I'm not sure how they will
stand up to vibration. The key points are:

1) VERY clean surface. Aluminum oxidizes quickly, and the oxides aren't
visible. You need to clean it JUST before gluing.
2) The glue needs to get a bite -- dead smooth surfaces are a problem.
3) You need a THIN glue joint.

Points 1 & 2 suggest you abrade the surface just before gluing. Points 2
& 3 suggest the abrasions should be very fine -- NOT coarse sandpaper. I
use really fine emery cloth. Point three is critical go all glues
(except those specifically made to fill gaps). In other words, CLAMP the
surfaces.

I've also found that not all epoxies work as well with aluminum -- I
haven't had much luck with 5 minute epoxies, or any of the ones sold in
tubes -- they're too thick.

Finally, the nature of the forces acting on your glue joint make a
differences. Because aluminum alloys are often soft and ductile, you can
sometimes get a "peeling apart" effect. I've found in most of my failed
attempts to glue aluminum, it was the physical arrangement of the joint
that was the real problem.

I've had quite a bit of success with a combination of thin, liquid
epoxies and one or two small pop-rivets. The rivets clamp the surfaces
very tightly (making a thin joint), and stop the "peeling apart" forces.
The glue provides added strength and prevents any loosening around the
rivets.

Good luck,
Bruce

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