If you aren't working in a production shop the holesaw style notchers work just fine...
I set mine up on one of my jig tables but it will work on any bench or table top you have handy. I usually run it with my 1/2" drill motor.
These pics show my Harbour Freight tubing notcher clamped to a 90* angle plate. This is simple to set up and doesn't require a lot of thought...
From the backside...
Cutting the first notch is the easy part. No orientation, no length to worry about. Just clamp the tube in the notcher and do the deed.
Cutting the second notch is where some planning needs to be done. Getting the LENGTH and the notch ORIENTATION correct is critical to having a usable part versus something to practice welding on...
To do the second notch I bolted a short piece of the mating tubing to another angle plate and use this to nest the "first" notch into while cutting the second notch.
This way I can establish the correct length AND notch orientation in one easy step... Set the tubing length between the outside diameter of the tubing and holesaw, in this case 23 inches, square up the jigs, clamp it all down and cut the second notch. Once it's set up any additional tubes will be identical to the first so measure twice and cut once...
Cutting the second notch...
Thanks for looking
Mark