I’ve bought a coax stripping tool, shown below. Also shown are my attempts at stripping coax. I finally succeeded in the far right photo, bottom example, which suited the plug I was using. The tool has two blades so it will cut the inner and the outer in one hit. You can set the blade cutting depths and the distance between the blades. This is a useful and relatively cheap tool. Well worth a go if you make up your own coax leads.
Have a look at the video below to learn how not to use a crimping tool.