Holding down the spacebar brings the lathe up to speed while left-click presses the tool to the block, carving grooves into its surface. The ‘wood chips’ that spew forth from the wound add quite a lot to the overall effect.
The wooden block seems to be made from a custom cylindrical mesh that’s been subdivided into segments along its length. Collision with the tool reduces the radius of the appropriate segment, while wood chips are pulled from a pre-created pool of objects (for speed) and given a new random rotation and velocity. The wood-grain texture is procedurally generated using a fragment shader.
three.js has a LatheGeometry which I’m guessing could be used to similar effect, there’s a nice ‘glass’ example that uses it on Chrome Experiments.
Despite my best efforts, I was unable to carve any swear-words, but I am confident.