The following are the instructions for the programme TubeMiter by Giles Puckett.
A tube mitering program for Windows to print on any printer.
My program deals in metric units. File/Settings... puts up a dialog box. You input: * Diameter (in mm) of tube being mitered * The wall thickness of this tube * The second tube diameter (the one it abuts up to) * The included angle in degrees. It paints the picture on the window, and File/Print... prints it on any connected printer. There are two curves - the dotted one is the template you would cut if the wall thickness were zero and the solid curve is the template corresponding to the requested wall thickness. If the mitered tube diameter is greater than the second diameter, then the second tube passes through two holes in the mitered tube. This situation is handled by continuing the template on the other side. Small gaps may appear in the curves; this is a known "feature" of the way the program works.
Additional note by Tony Foale 25/01/2001
The actual programme states that the tube to be notched must be smaller than or equal to the other tube. As mentioned in the above text this is not so. The tube can be smaller or larger. I've checked this and it functions fine either way.