(This text is a preliminary draft, comments are welcome).
Kvarnbokvarn was mentioned in text as early as 1316, but the current building is probably from the 1700s, and the workings inside from the 1800s. In the 1930s a Francis turbine was installed to improve efficiency, and there are signs that an electrical generator may have been added, before the mill stopped being used in the 1940s. Over the centuries the workflow will have changed a lot, but here I will try to give a general idea of how the mill probably operated in the earlier days.
Workers would arrive from the surrounding farms with their harvest in horse drawn carts, and if necessary the horses would be allowed to feed and rest in the stables beside the mill. The main crops would have been rye and oats, and would probably have been threshed to remove the husks before delivery to the mill.
The sacks would then be hoisted to the upper floor through a trapdoor, drawn by a rope that was wound around an axel that could be connected to the water power through a clutch mechanism that was engaged by pulling on a wooden lever by the trap door. Perhaps it would be stored there until the spring floods provided more water power, as it's a bit of a mystery how they got enough water power from the small Hågaån that drains Fibysjön 15 km north west. Above the bridge there is an open area which was presumably flooded to become the mill pond, but it's still hard to imagine how it could drive such a large mill for long. Some farmers would also have stored the grain at home, delivering it later in the year when prices were higher.
The grain would then be put through a filter upstairs, and then sent back down to the ground floor through funnels.
Oats might then be made into flakes using the smaller rolling machines in the middle of the room.
But the main purpose of the mill was to make flour, and for this the grain would be funneled to the middle of one of the four large mills. Each mill consists of one stationary millstone on the floor, with a second stone, weighing more than a ton and spinning at around 100 rpm a few millimeters above it. The stones must be extremely well crafted so that they spin without wobble, and have a constant separation as they spin. They must be kept close enough together to crush the seeds, but mustn’t touch each other as they would quickly wear out, and also make sparks that could ignite the dust which would have filled all the rooms. Their separation could be controlled by a wheel beside the mill that turned a threaded bar that lifted the upper stone, and are also held apart by the seeds themselves, whose feed could not be allowed to cease for this reason. The milled flour would exit from the edges of the stones, and would be led down wooden tubes into sacks in the basement. From there they were probably passed through the windows into the 'alley' alongside the building. Some stones were cast from mixture of grit and cement, others cut from solid stone, usually limestone or sandstone. An example of each sits outside the mill, serving as coffee tables.