It's damn hard to get a good structural bond between epoxy and alminum. As many have pointed out, it's the oxide coating on the surface that's tough to get rid of. Luckily in this application, the epoxy/aluminum bond is not structural--I would think almost any glue would work that would create a solid interference fit any not degrade over time.

I like the idea suggest below. A lot of times we get tied into the idea that we have to use the materials that we are familiar with. Generally that's a good thought, but sometimes there are simplier, cheaper and stronger ways to do things.

: BTW: why cant you glue the insert in and: drill, insert and rivet a pin, file
: the pin to the surface of the tube?