Tennis ball slippers help?

Hello fellow educators,

I have a librarian colleague who is trying to figure out the best way to cut into tennis balls to turn into covers for classroom chair feet. I realize that this is a rather niche issue, but I am wondering if anyone has any ideas? Thus far we have brainstormed/tried:

- using a drill press (the friction melted the tennis ball)

- exacto knife to cut slits (almost removed our thumbs)

- possibly using a saw to cut the tops off??

Any ideas that do not require a great deal of power tools would be extremely appreciated!!