Good tips
, if you are handy and have a lathe, try this..
Rig up a V block & clamp on your toolpost, bottom of V should be on Centerline.
Mount your holesaw, flycutter, rotaBroach, etc in the chuck or better with taper adaptor to spindle.
Clamp tube in v block, adjust angle & clamp toolpost.. use handwheel of carriage to feed tube into cutter..
I bet you never go back to the drill to notch after that..