How can I make a pattern to cut a metal pipe at 45 degrees?

You are describing exactly what I need. We are doing the job in the field with a torch and DC welder. I once had such a pattern, but don't remember how to do it. My first approach was to wrap the pattern around the pipe then mark it the length (horizontal) of the diameter from that line (vertical). So the pattern would be a triangle. But upon cutting the 45 degree plane I ended up with a point at each end instead of smooth curves.
Karl Townsend wrote:
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That's it! I was making the edges straight. The normal curve fits much better! Thanks!
R. Zimmerman wrote:
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I don't have a clue as to whether this might apply to mitering pipe, but it might be worth trying, if not for this application, then maybe something else.
I saw a method to create an oval (of no critical size) using 2 nails in a board and a piece of string tied into a circle.. on The Yankee Workshop maybe. An oval is an ellipse to me, and the opening in a mitered pipe is similar or the same? Yeah, I'm not one of the sharper pencils in the box.
Two nails are tapped into a board, leaving them standing above the board. A piece of string is tied into a circle that fits over the nails, but has slack. As a pencil is used to draw a line inside the string (while keeping the string taut), an oval is created.
I wouldn't have any idea as to how to predetermine the ratio between the distance between the nails in relationship to how big the string circle should be, to then be able to predict the resulting drawing.
If this method was feasible for creating an oval the same size of the mitered pipe opening, then a thin template could be made to slip onto the pipe, and position it at 45 degrees for the placement of the cutting line.
Unrelated to the above, but it occurred to me that a specific length of string would be the cut line for the miter angle, but how to get it to the right location on the pipe is a mystery to me.. float it in water, I guess.
Make a big profile duplicator, like those tools for cutting material to match a profile (with a long series of parallel pins in a holder), but that's a big tool for 12" pipe.
Cut the pipe, trim the opening to fit a flat surface, check the angle, adjust to 45 degrees. Slit a section of the pipe when the angle is correct, and use the slit section as a marking gauge for other cuts, or make a thin flat template with the opening and use it for a marking template for subsequent cuts or trimming/adjusting.
Whichever one of the 469 commonly known or unofficially registered ways used to to skin a cat, it still tastes the same.
WB ...........
Petrovitch wrote:
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Wild Bill

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