A few years back I asked this question and now do you think I could find the answer nooooo....
Anyhow I have a tube that will get hammered down on the end, and a hole drilled in it so that it can be bolted to stuff / other tubes. Sort of like what you would see at a jungle gym in a playground, the geodesic dome structures that are made of tubing and crimped at the end and bolted together.
I am at a loss as to how to model this, just know I did it years ago at a place I no longer have access to the models :(
Ben.