Pat′tern.
1. A piece of card-board, sheet-metal, or thin plank corresponding in outline to an object that is to be fabricated, and serving as a guide for determining its exact shape and dimensions; such are employed by workers in leather, textile fabrics, and other thin materials for cutting out work, and also by wood-workers for laying off the outlines of objects of irregular form which are afterward shaped by the axe or saw. (See Template.) Pattern-pieces or gages are largely used in making special machinery, such as rifles, sewing-machines, American watches, and numerous machines in which all the parts are made separately by gages and then assembled. The system is known as making by gages and assembling. See gage; assembling.2. (Fabric.) A design of figures, woven in cloth or printed thereon.
3. (Founding.) The counterpart of a casting in wood or metal from which the mold in the sand is made. When dry-sand or loam-cores are used to form the cavities in a casting, projections of suitable size and shape are affixed to the pattern to secure such cores in place. See print. Patterns are often made in two parts, sometimes in several parts, held together by steady-pins or dowels. Straight-grained pine or mahogany is preferred for patterns of this kind; screws rather than nails are employed for joining the pieces. Foundry patterns are made somewhat tapering in those parts which have to enter deeply into the molding sand or loam, in order to facilitate their removal; this taper may amount to 1/16 or 1/8 of an inch to the foot, and in some cases even more. Ordinary iron shrinks about 1/8 inch to the foot in cooling; brass, 3/16 inch; and this must be allowed for in the pattern. For this purpose a contraction rule is employed, giving measurements about one per cent in excess of the true length; this avoids the trouble of calculating the extra dimensions to be given the pattern in each particular case. Wooden patterns should be well oiled and varnished. This preserves them and assists their free delivery from the mold, which is farther insured by rubbing them with black-lead. In their construction, sharp interior angles should be avoided as tending to cause a breaking down of the mold at that point and weakening the casting. Patterns, especially for small castings, are sometimes made of metal. These have the advantage of being more durable, but if of iron require to be taken good care of to prevent rusting. See list under founding; molding. For machine for pattern-making, see numbers of American Artisan for May and June, 1874.
