Didn't know exactly where to put this, but figured this forum would be appropriate.<O</O
<O</O

If you've ever tried to use a chop saw to cut a notch in one pipe to sit flush on another, figuring out the angles to cut is (at least for me) a guessing game. There are a few guides out there that have angles for a few pipe sizes, but I wanted a universal formula that can work on any pipe size. I think I saw an online calculator somewhere, but the last thing I want to do when I'm working in the garage is run back in the house and fire up the computer.<O</O<O</O

Long story short, I sat down and worked out the trigonometry:<O</O

The bottom plot is a zoomed in section of the top plot for the portion where the curve isn't as linear.

The angle is between a straight cross cut and the notching cut from the point of view of the edge of the pipe (if that makes any sense) - so 0 degrees is a straight cross cut, 5 degrees would be a slight point, 15 degrees a little sharper, etc.


The ratio is of the ID of the pipe being cut divided by the OD of the pipe you want the the cut pipe to sit flush against. In the end, this ratio is the only one that matters when determining the cut angle.

Note that the angles are if you want to join two pipes at a 90 degree angle. If you want to have an angled joint, add that angle to one of the cuts and subtract it from the other. When making the cuts, the two should come to a point on the centerline of the pipe being cut.

 

Details behind the charts for anyone interested: