Stamp mill

Author:wikipedia   Post Date:2009-7-9

A stamp mill (or stamp battery) is a type of mill that crushes material by pounding rather than grinding, either for further processing or for extraction of metallic ores. Breaking material down is a type of unit operation.

Stamp mills were used in early paper making for preparing the paper-stuff (pulp), before the invention of the Hollander beater. They were used in mining for breaking ore, and in oil-seed processing for prior to pressing the oil from the milled seeds. Early mills were water powered but mills can be steam, water, or electric powered.

Cornish stamps are stamp mills that were developed in Cornwall for use in tin mining in around 1850. Cornish stamps were used to crush small lumps of ore into sand like material. Constructed from heavy timber or iron lifters with iron "heads" at the bottom were raised by cams on a rotating axle, and fell on the ore and water mixture, fed into a box beneath. The heads normally weighed between 4 and 8 cwt[vague] each, and were usually arranged in sets of four, in timber frames. Small stamps were commonly powered by water wheels and larger ones by steam engines.

Californian stamps were based on Cornish stamps and were used in the Californian gold mines. They were more rapid in action, and the heads and lifters were made to rotate so that they wore more evenly. The other advantage of the Californian stamp was that a single head could crush 1.5 tons of ore as opposed to the Cornish stamps which could only crush 1 ton.

Arrangement

A stamp mill consists of a set of heavy steel (iron-shod wood in some cases) stamps, loosely held vertically in a frame, in which the stamps can slide up and down. They are lifted by cams on a horizontal rotating shaft. On modern mills, the cam is arranged to lift the stamp from the side, so that it causes the stamp to rotate. This evens the wear on the shoe at the foot of the stamp. As the cam moves from under the stamp, the stamp falls onto the ore below, crushing the rock, and the lifting process is repeated at the next pass of the cam.

Each one frame and stamp set is sometimes called a "battery" or, confusingly, a "stamp" and mills are sometimes categorised by how many stamps they have, i.e. a "10 stamp mill" has 10 sets. They usually are arranged linearly, but when a mill is enlarged, a new line of them may be constructed rather than extending the line. Abandoned mill sites (as documented by industrial archaeologists) will usually have linear rows of foundation sets as their most prominent visible feature as the overall apparatus can exceed 20 feet in height, requiring large foundations. Stamps are usually arranged in sets of five.

Some ore processing applications used large quantities of water so some stamp mills are located near natural or artificial bodies of water. For example, the Redridge Steel Dam was built to supply stamp mills with process water.

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