how can I angle this round tube 15 degrees down
You need to post the component parts of the assy as well.
Angle it down in respect to what? Do to change the angle of mating parts so the tube move 15°? (in some direction) Or, do you want to curve the tube down 15°. Or, do you want to cut the tube at 15° and make the mating parts oval to match?
(Kelvin, you can open the assembly in design review mode without the components)
If what you want is this:
then you just have to use lofted bend with two sketches containing the profiles. I attached you the file so you can see it . Sorry if its in spanish, but i think you will get it.
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