Hammer mill

A hammer mill, hammer forge or hammer works was a workshop in the pre-industrial era that was typically used to manufacture semi-finished, wrought iron products or, sometimes, finished agricultural or mining tools, or military weapons. The feature that gave its name to these workshops was the water-driven trip hammer, or set of hammers, used in the process. The shaft, or 'helve', of the hammer was pivoted in the middle and the hammer head was lifted by the action of cams set on a rotating camshaft that periodically depressed the end of the shaft. As it rose and fell, the head of the hammer described an arc. The face of the hammer was made of iron for durability. These mills, which were original driven by water wheels, but later also by steam power, became increasingly common as tools became heavier over time and therefore more difficult to manufacture by hand. The hammer mills smelted iron ore using charcoal in so-called bloomeries (Georgius Agricola 1556, Rennherden, Rennfeuer or Rennofen: from Rinnen = "rivulets" of slag or Zrennherd from Zerrinnen = "to melt away"). In these smelting ovens, which were equipped with bellows also driven by water power, the ore was melted into a glowing clump of soft, raw iron, fluid slag and charcoal remnants. The iron was not fluid as it would be in a modern blast furnace, but remained a doughy, porous lump mainly due to the presence of liquid slag. These lumps of sponge iron, known historically as "blooms" were initially compacted by hand using a sledgehammer. After that they were forged several times, usually with the trip hammer or with sledgehammers until all the slag and charcoal had been removed. For that, the iron was heated in another forge oven or smith's hearth. The iron could then be directly used as soft iron. A further improvement process, such as fining as used in blast furnace operations, was not needed. The resulting coarse bar iron was then further worked externally e.g. in special, small hammer works (Zainhammer) into thin iron rods, (e.g.