Pattern making dates back to the time when the first article was made from molten metal for the use of man. The pattern must precede the making of its metal counterpart, and is therefore the first subject to be treated in the working of metal.
The pattern maker is essentially a worker in wood, though, where many castings are to be made from the same pattern, the final or working pattern is made of metal. These metal patterns are very serviceable, and leave the sand more easily and cleanly than those made of wood. Metal patterns are always necessary when the work is of a delicate or very light character. In all such cases, however, the first pattern from which the metal pattern is to be molded is made of wood, allowance being made for double shrinkage, and, when necessary, for double finish. The necessity for this will be clearly explained farther on.
The pattern maker should possess a practical knowledge of the properties of metals. First of all, he must understand the shrinkage of metals, that is to say, how much smaller the cold casting will be than the molten mass as it flows into the mold; he should know what the strength of the metal is; he should be familiar with the relative rapidity of cooling, so that internal stresses in the body of the completed casting may be avoided as much as possible; he also should know enough about the practical work of the molder to decide upon the peculiarities of construction of the pattern for any given piece.
The pattern maker must be sufficiently skilled as a draftsman to lay out, without the assistance of the designer, the drawings of the piece to be made. This qualification is one of the most important. It is very true, however, that there are many good pattern makers who do not possess all of these qualifications.
The drawings furnished the pattern maker are usually on a small scale. In order to work to the best advantage, he must reproduce a part or all of them at full size, as working drawings. To do this in such a way that the lines and curves of the finished pattern shall be graceful and artistic in appearance requires the same nicety and precision of workmanship that are demanded in the drafting room, and it is essential that the pattern maker have the same complete knowledge of the principles involved. To the extent, then, of being able, when necessary, to make a full-sized drawing of the article to be made, the pattern maker must be a draftsman.
In large establishments, where all the work comes to the pattern shop in the form of carefully executed drawings, the pattern maker is the means of putting the ideas of others into tangible shape. In smaller places, where no draftsman is employed, the pattern maker will be called upon to work out the designs for which he is to make his patterns, and he thus becomes the real designer.
Finally, the pattern maker is seldom required to make two patterns that are identically the same. His work, therefore, is varied, and he must be prepared to apply to the solution of new problems that arise such principles as he may already have learned.