Hey all I'm building some duct work with about 2" pipe that has a fan on it. The fan end has a square opening
3 1/2" squared opening. And the pipe circumference is 7 1/2" od I'm just wondering if there is some sort of formula /procedure to lay this out so it looks right rather than me just notching hammering and filling with weld. I assume its similar to laying out an orange peel cap end. Just can't fund anything on this. Thanks