Pipe/Tubing Fit

[Kevin Sevcik]

My materials prof loves talking about this. Basically, you can get 2 of the 3, but not all three. OD and thickness means you get a minimum wall thickness all the way around, but the inside can end up kind of wavy. I definitely wouldn't expect it to hold a .005 tolerance without some machining. But then, I'm still an engineering student, so I could be wrong.

[Jason Kixmiller]

As for turning down one end, most lathes have a chuck that will allow the material to be passed through the entire machine. If the lathe you hope to use has the capability to handle the diameter you are using, this is probably the easiest method. Be very careful with the extra tubing that is spinning outside the lathe...it can be easy to forget but will remind you that it's there very quickly! For the slot, I would use a V-Block set-up in a standard vise to hold the pipe on its sides allowing you to run an endmill through one side of the tube.

[Al Skierkiewicz]

Sanddrag,
It depends on what you plan on using it for. Outside, in the elements, those tolerances will quickly close down and you won't be able to pull stuff apart. It also will depend on what you use to cut the tubing to length. A hacksaw or tubing cutter will distort the cut end where a cutoff saw might not. A slight bend in the tubing will also close down the tolerance and since this pipe is not handled with care in hardware stores, expect a few dings here and there.
The ARRL Radio Amateurs Handbook has a table on aluminum tubing standard sizes for 6061-T6 tubing and good discussion on telescoping tubing sections for antennas. The current book should be on your library shelf. The table is in the chapter on antenna projects and will also show methods of joining sections and calculations for sag, overlap and windload if you need that info.