So, I'm a bit curious here: You hold a new/sharp razor in your hand while the lathe is turning a very slow speed? Or, do you hold the razor in your hand and turn the lathe slowly by hand? Maybe a photo of how you do it?
I install a number of tips for friends, and myself, of course. I'd be interested to try to turn the tip to size with the lathe tooling ..... just so I could compare the two methods.
Unless you are VERY familiar using a razor to trim a tips od using the lathe running...then I SERIOUSLY suggest not trying it. Extremely easy for Mr. Murphy to have the tip grab the blade and cause someone to loose a finger...or two. If you really want to learn more then just search for the Sniper install method...Tony may even have some info from Tiger. They offer a special blade too that may make it easier/safer...I'm not sure as I haven't tried it. I think you can find some videos in your search as well.