When the tip of you kendama wears down to a flat piece of poo(that is to say if you DID'NT GLUE YOU TIP.....which you SHOULD!) Please for the love GOD! don't just go at it without reading this PLEASE PLEASE PLEASE.
Taking any ol sharpener to your kendama can leave you with a long ugly pencil type tip all long and uneven and such. if you go to any hardware/lumber shop they have sharpeners called carpenters pencil sharpener there for the flat ones, anyway. Don't put the tip all the way to the end of the sharpener put it in about a third maybe halfway. It will make the point smaller, more like the way it came originaly.
you might not care, im just anal about that kinda stuff.