"Paul K. Dickman" wrote in message
...
I gluing 2 pieces of metal together there a 3 things to remember;

#1 surface area
If you can use a 1" sq plate with a hole in the corner instead of the
standoff it will have 20 times the glue joint area.

#2 tooth
Rough up the joint surface with 80 grit sandpaper, it increases the
surface area and randomizes the shear angle so it will not pop off easily.

#3 Chemical coupling
Epoxies work best when they are able to chemically bond with the
metal.
This is tough on aluminum because the oxide surface on aluminum is almost
completely inert and will form immediately on exposure to air. The
solution
is to put a drop of epoxy on the area to be glued and rough the surface of
both pieces to be glued with sand paper through the epoxy. This protects
the
surface from exposure to air. Then, wipe off the dirty with epoxy with a
DRY
paper towel and apply some fresh clean epoxy and bond as usual.

Paul K. Dickman

Dave Marsh wrote in message ...
snip

So far I've tried an epoxy ("plastic steel" by Draper) with the hex
spacers.
Initially it seemed ok, but with a small amount of leverage the spacers
came
away.

Could someone please suggest whether I would get better adhesion on the
anodized aluminum with the zinc screws, stainless steel screws or the
nickel-plated hex spacers? What epoxies would you recommend? I've also
been
advised that curing the epoxy will improve the adhesion - does this make
a
big difference?

Many thanks,

Dave


Many thanks Paul. That all sounds like very solid (sic) advice. I did sand
down the surface of the aluminum but not in the way you described. I will
try that next time. The plate idea is a good one, so I'm thinking of putting
a short countersunk machine screw through a small plate (unfortunately it
will have to be more like 3/5" square due to lack of room) and then gluing
the plate to the front panel. I can then screw a spacer on to the screw.

Dave