I came across this online pipe joint template calculator and thought it was interesting: http://www.harderwoods.com/pipetemplate.php. You can use this calculator and print the template onto a sheet of paper to make your own dust collection joints.
Yup. That's a great template and a great site. I used those templates extensively when I ran the dust collection in my shop. Some of my tubing was larger than the max size in the program, and Mr. Harder was kind enough to modify his site to include my larger sizes. A class act and great guy.