On 21 Aug, 01:33, (Steve Firth) wrote:
Dave Plowman (News) wrote:

I need to secure a boss made from aluminium rod into a hole made in the
wall of an aluminium tube. Of course welding would be ideal - but there's
little load on it. And I'm not sure I can be bothered finding an aluminium
welder. Unless I could do it myself with my MIG. Which I'm not much good
with on steel. ;-)
Car body filler? Epoxy? Any special precautions?

http://www.weldguru.com/braze-aluminum.html

You can use Araldite, but you need to thoroughly de-grease and I find it
better to abrade away the surface oxide before applying the adhesive. I
once made a whole load of microscope slide racks from aluminium extruded
sections and glued them with araldite. It was obvious which ones were
not succesfully glued. A slight tap on the desk and they fell apart.

I was told when I worked with a group that developed composite structure
for aircraft that epoxy glued aluminium degrades fairly rapidly over
time and that over-the-counter epoxy gues really don't bond well to
aluminium. The preferred adhesives for aluminium are a hybrid epoxy
adhesive such as epoxy-nylon and specialist polyurethane glues. Some of
these glues require special primers or activators to be applied to the
surface before bonding.

If I wanted to make a permanent job I'd braze it, using the appropriate
aluminium brazing rod.

I was building a control panel of Aluminium recently which had plywood
inserts and decided to try ordinary polurethane wood glue - 5 minute
setting gunable type . Totally successful. I then needed to attached
a small Al bracket to carry a connector and again used this PU glue,
finding it did the job perfectly for an Al to Al bond.

Now having read the above post about epoxy glued aluminium degrading
over time, I'll might remember to have a look in a year's time to see
if the bond is still OK.

Rob