Using a CD jewel case, some magnets and a 12-volt air compressor, you can build an elaborate Tesla turbine sharpener for pencils you probably don't even use. Oh, did I mention it could kill you?
Indeed, the instructions point out that a strong enclosure is required just in case the whole damn thing explodes in your face. But, in the end, your risk will be rewarded with a machine that takes down a pencil at over 2200rpm. Hey, why not scale this thing up for a wood chipper? Put the whole neighbourhood at risk. [Hacked Gadgets]