MACHINE ENGRAVING. A process in volving the use of a machine to engrave wood, metal, or stone. Machinery has been devised which will carry on many of the manual opera tions of an engraver and produce regular tints, geometrical designs. and other symmetrical pat terns with greater accuracy and far more rapi.1 ity than would be possible by hand work. The first machine of this description was invented by Wilson Lowry, and was known as a ruling machine, being employed to engrave such me chanical features of a plate as the plain back ground, skies, etc. In most machines for engrav ing, the tool is so arranged that after each cut it can be moved a certain definite amount so that at the next stroke a parallel line is cut at a regular distance from the last. In wood-engrav ing the breadth of the tool, or the depth to which it is allowed to cut, regulates the distance be tween the lines and the nature of the tint. For metal work the machine may be fitted with a highly tempered steel cutting tool. though in the case of engraving copper plates the latter are usually coated with varnish which is scratched by the tool and eubsequently etched by acid.
In the latter ease the intensity of the action of the acid will regulate the thickness of the lines. When it is necessary to engrave on stone with a machine, the cutting tool has a diamond point. and the depth of the cut is regulated by means of weights on the tool-holder. The most min plex engraving is executed wholly by machin ery, and is employed in the manufacture of bank-notes, bonds, stock certificates, and other papers which it is necessary to protect with a peculiar and individual pattern. By an elaborate system of gearing the cutting tool so moves that it will execute a certain number of symmetrical motions and thus produce elaborate geometrical scrolls and patterns. On such a machine it 1s possible to make many combinations of figures for a pattern, but it is impossible to reproduce any given design once it has been traced. See