Notching a piece of tubing can be frustrating, especially if you have a compound joint and/or a severe angle. I recently came across a tool that makes these type of joints a lot easier. Even though a standard joint is often more easily achieved using a standard tubing notcher, they don't always work for every situation. These tools made by pipemaster can be used to mate any piece of tubing or pipe 1/2" up to 12" diameter to any shape you need to mate it to.
Another method that I have used in the past with success is the online Tubing Coping Calculator. With this online tool, you input the values such as the size of the tubes you are mating together, angle, and the thickness of the tubing and it gives you a template that can be printed and cut to wrap around the tubing to mark your cut. Below is an example of a pattern that this tool will produce.
