I use a single edge razor blade to cut mine. To get a square end; I made a jig by drilling a hole in a piece of wood (needs to be a snug fit and square to the surface), slide the tube in the hole and use the wood block surface to slide the razor along and push through the tube. I then us a lighter or candle and twirl the end of the tube (free hand) close to the flame. A small burr forms in ID and I remove this with an Exacto knife. The whole process takes a few seconds. The key to a uniform, good looking flare, whatever method you use, is to get a square end.