Well, first off if you never worked, or replaced a tip, the layered ones can be a pain to work with. When you take a 14mm and cut it down to 11.75mm, the tip will seem really tall, so you might want to shorten it also. It's very hard to cut a layered tip down that much by hand, and get it even, and round, but it can be done. These tips are TOUGH!
*After selling my lathe, I now use my 1/2" multi speed electric drill, secured in my vise, with the right pin chucked in it for whatever shaft I'm working on. Don't laugh!, I can adjust the speed, lock the trigger and it works just like my lathe did without the live center, or steady rest.
When I do them, I glue the tip on dead center...I use super glue gel, then I use a razor knife to trim it to the ferrule. I learned this from Leonard Bludworth at the SBE a million years ago

. Then
I use a flat metal file to smooth and shape the tip. You can also use one of those cue cubes for shaping. Then I use some 400 wet dry sandpaper til real smooth, then burnish with a piece of leather, or hardwood.
>>>>Practice a few tips on a cheapy K-mart cue.....then on your player!
hope that helps, Gerry