I am not sure why there is not a large crayon sharpener (up until now) on the thingiverse.

http://www.thingiverse.com/thing:273589

I obviously have the need for one so I designed and printed it.  I am using a standard razor blade and a screw I had laying around.

In case you are wondering… Nope, I don’t get it perfect the first time here is my first and second attempt.  The third one works great though.

Iteration 1 and 2