This is a tool I designed to chamfer the ends of PTFE tubing. I was having issues with some PTFE connectors where the filament would catch on the edge of the tube and cause overload errors. The chamfer angle is approximately 70 degrees from horizontal. There are two holes for the tube: the hole near the tip of the blade is for chamfering the inside, and the other hole is for chamfering the outside of the tube. The outside chamfer is useful for sliding the tube into custom connectors that are a tight fit. I have tested it with both the Capricorn tube and Bambu tube.

For assembly, you will need:

2x - 3x M2 screws 8-10mm in length.

1x #11 exacto knife blade, https://www.amazon.com/Profession-Modeling-Scrapbooking-Stencil

In the model pictures I only used 2 M2 screws, the one at the top goes through the hole in the blade, and the one in the middle is to lock the blade in place. There is an optional third screw hole that pushes against the back of the blade if you have issues with the blade moving around when cutting. The cutting edge of the blade is supposed to point outwards. 

To use the inside chamfer, just slide the tube in and twist clockwise, looking at the base of the tool. To use the outside chamfer, slide the tube in and use your finger as a hard stop to prevent the blade from taking off too much tube. For this tool to work properly, you need to take only a very small bit off at a time. Too aggressive of a cut and you will end up spiral-cutting your tube. The blade has some room for adjustment to help improve the quality of the cut. I would recommend getting a test piece to practice with first, before cutting a tube you have already cut to a specific length.