Thank you. That totally did exactly what I wanted.

And thanks to everyone who responded. I don't think I made it exactly clear that I'm rotating the pipe (x axis) under the torch and the torch only moves across the length of the pipe (y axis). I'm not sawing across it like a chop saw would at some angle.

I took a 1.75" circle in Rhino, extruded a surface, rotated it 15 and 60 degrees, split it, UnrollSrf and ...BAM! ...just what I wanted. Now I have a flat, sine-wave-looking curve that I can use to tell my torch how to cut the pipe.

Also, it is true that I won't get a beveled edge on the cut like you would on a tubing notcher, but this is mating to a flat surface and the wall thickness is like 13 gauge, so whatever gap it has will be minimal and completely acceptable for my application. UnrollSrf was exactly what I was looking for. Thanks.