Millstone

The Millstone handles milling recipes: one input, one or more outputs, sometimes with a bonus chance. Wheat gives one Wheat Flour, plus a 25% chance of two more and a 25% chance of a seed. Flowers give two dyes, sugar cane two sugar, a bone three bone meal, wool one string, gravel one flint and sandstone some sand.

It handles one item at a time: a whole stack put inside is ground one item after another.

The Millstone takes rotation in two ways: a shaft from below, or a cogwheel placed against one of its sides, since its rim meshes like a small cogwheel. That is what the animation shows: rotation comes in through a neighbouring wheel, and the top stays free for input.

It uses 4 SU per RPM, so a single small water wheel can run it at 64 RPM.

Items go in through the top. By hand, just throw them onto the millstone and it swallows the item that lands. For automation, a funnel, a hopper or a chute above it keeps it fed. Grinding time depends on speed: each recipe has a duration (150 for wheat, 50 for a flower, 250 for gravel), and the millstone removes RPM ÷ 16 from it every tick. At 32 RPM one wheat takes about 3.75 s; at 256 RPM, half a second.

For a real production line, empty the millstone with a funnel on its side, a hopper underneath, or a Mechanical Arm. In the animation, the products come out onto a Mechanical Belt that carries them away. A classic early chain: harvested wheat, a millstone, flour, then dough with some water, and finally bread in a furnace.