MILL, the term given to the apparatus used in the grinding of corn into flour, and hence applied to similar mechanical de vices for grinding or pulping other substances; e.g., coffee-mill, powder-mill. "Mill" was first used of the building containing the apparatus, frequently with a word attached descriptive of the motive power ; e.g., wind-mill, water-mill, etc. It was not the early word used of the actual grinding mechanism. The old hand mill was known as a "quern" (see FLOUR). The word mill is also applied to many mechanical devices by which raw material is transformed into a condition ready for use or into a stage pre paratory to other processes; e.g., saw-mill, rolling-mill, etc., or still more widely to buildings containing machinery used in manu factures ; e.g., cotton-mill. In mining it is applied to various machines used in breaking and crushing the ore (see ORE DRESSING) .
In the engineering industries milling machines constitute a very important class of machine tools, the characteristic of which is that rotary cutters are employed for shaping the metal (see Tools). In coins the "milling" is the serrated edge, called "cren eling" by John Evelyn (Discourse on Medals, 1697, p. 225), which is formed on them to prevent clipping and filing. Coins made by the old process of hammering were apt to have irregular edges which invited mutilation ; but the introduction of the screw press, which came to be known as a mill (cf. W. Lowndes,
Amendm. Silver Coinage, 1695, P. 93), permitted the production of a regular edge with serrations which in consequence were termed milling. This machine also enabled legends to be impressed round the edges of coins, such as the Decus et tutamen suggested by Evelyn (see W. J. Hocking, Catalogue of the Coins, etc., in the Museum of the Royal Mint, 1906). It was invented about the middle of the 16th century, and has generally been attributed to Guyot Brucher (d. 1556), who was succeeded at the Paris mint by his brother Antoine. Introduced into England by one Eloye Mestrel in 1561, it was used for years, and was then abandoned owing to the opposition of the mint officials to Mestrel, who was executed for counterfeiting and striking money outside the pre cincts of the Tower of London; but it was again introduced by one Peter Blondeau in 1662, when it permanently superseded hammering. In the United States of America the term "milling" or "milled" is applied to the raised edge on the face of the coin; this is known in the British mint as "marking" (see MINT).