PATTERN MAKING. 



PART I. 



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. 



Qualifications of the Pattern Maker. 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 moulded 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 mould; 

 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 moulder to decide upon the peculiarities of 

 construction of the pattern for any given piece; and he must be 

 sufficiently skilled as a draftsman to lay out, without the assistance 

 of the designer, the drawings of the piece to be made. It is very 

 true, however, that there are many good pattern makers who do not 

 possess all of these qualifications. 



The last-mentioned qualification is one of the most important. 

 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 



