Pattern
The Encyclopedia of Founding (1892)
In moulding, the pattern is a counterpart of the casting required, from which the moulder obtains an impression in sand or other plastic substance. This impression obtained, it remains to fill the space, previously occupied by the pattern, with molten metal, which when solidified is a true representation in metal of the pattern supplied, less the shrinkage. Patterns are sometimes called models, from the fact that the modeller furnishes patterns for both the brass and iron foundries made from plaster or stucco. Wood patterns made by the pattern-maker are by far the most numerous, including as they must patterns for nearly every cast piece used in producing the multitudinous examples of structural, machine, and engine work. Very much of moulding is now accomplished without a full pattern, when a good understanding is maintained between the moulder and the pattern-maker. By a judicious arrangement of strickles, making-up pieces, and sweeps, castings are very often made almost exclusive of a pattern altogether; but this only occurs when the ability of both artisans is above the average. Machines for moulding gears have reduced pattern-making for wheels to a fraction of what it formerly was, and numerous other castings may, by the aid of a segment and perhaps some core-boxes, be made by them as readily. Besides patterns in iron and brass, numerous others are the production of the modeller, made in stucco or plaster, and not a few are, with the aid of template and sweeps, made in loam by the moulder himself. See LOAM-PATTERNS; BACKING-OUT; SPINDLE.
What Has Changed in the Last Century
The 1892 account's core physics still holds: a pattern is a counterpart of the wanted casting, and the metal shrinks as it cools, so shrinkage allowance remains the patternmaker's first concern. What has gone is the trade itself. Where the 1892 writer assumed a skilled wood patternmaker working with strickles, sweeps and loam, patterns today are usually cut from resin board or aluminium by computer-controlled milling machines from a 3D digital model, and since the 1990s sand moulds and cores have been printed directly by binder-jetting machines, so many castings are now made with no physical pattern at all. The apprenticed patternmaker, once among the best-paid men in the foundry, is one of the scarcest crafts in industry.
Written for this edition, 2026.