Whatever the general method of classifying the drawings, each drawing may carry more than one part, tho in some systems only one part is put upon each drawing. Where more than one part appears on a sheet each may be identified by a part letter. Thus, in such a system, K 24,689-A might signify part A on drawing 24,689 of the class of product indicated by K. This identifies the part beyond question, mak ing it possible to charge with accuracy all labor and material that enters into its production.
12. Drawing lists.—In most well-organized shops using methods of this kind, the engineering depart ment originates the directions governing the construe tive features of the work, and turns over to the con struction department full drawings and specifications in such detail that every part may be identified, not only during actual construction, but for all time, so long as the drawings are existent. In highly devel oped systems a drawing list, Figure 5 (page 55) , ac companies the drawings and specifications. Such a list constitutes a complete inventory of the parts that are to be made, and is an index to the drawings and lists, where the parts may be found in detail. Thus in Figure 5 the number of the drawing and that of the part or piece, are listed, the material of which the part is to be made is noted, and the number of the parts required is given. Reference is also made to the en gineering and other specifications that accompany the drawing. Figure 5 illustrates a system which used the Dewey decimal method for numbering drawings, but which uses a combination of letters and integers for other documents, such as tabulated data and en gineering specifications.
It will be noted that such a method allows the free and convenient use of any one part in the construction of any machine, whether designed originally for it or not, since identification is complete. Thus, in Figure 5 the armature and field are taken from one series, the shaft and bearings are taken from other series, and still other parts were made originally for other classes or sizes of the same type of machine.
The nomenclature given in Figure 5 has been taken at random, but it is a probable combination. In well standardized production such lists may be printed in outline and the data filled in by hand. Thus in Fig ure 5 the data that would be so filled in is indicated by script. It will be evident that the shop orders
governing the production of the machines, as a whole or in part, as the case may be, and the shop returns recording the details of such production, can be made out with the assurance that, so far as identification is concerned, the correct labor and material charges will be recorded against the cost of the part concerned.
13. Mnemonic and number systems compared.— The relative merits of mnemonic symbols and numeri cal identification should be noted. No doubt, in the cases where the number of items is small and where it is desirable to remember departments or operations, the mnemonic system is useful. For this reason it is often used to identify departments and operations. It is also used to identify expense orders. Thus all charges against buildings can be carried in account B, and all charges against power, heat and light, against account P. H. L. In large factories, how ever, where it is necessary to separate the expense into many items, it becomes necessary to use numbers. Thus the labor report, Figure 25 (page 293), lists the expense by numbers, while the direct labor is charged against the letters which identify the several classes of product.
Obviously, the degree of detail needed in the nomen clature of a factory depends entirely upon the charac ter of the enterprise. In simple, continuous indus tries few details are required in the nomenclature, while in large, intermittent industries it may be neces sary to go to all the detail which has been described. Whatever system is adopted it should identify each part beyond a doubt, and it should be capable of ex tension as the industry expands. To change the sys tem of nomenclature and identification is always a troublesome problem and one that can often be avoided by a little foresight.
It is important to have clearly in mind the prin ciples that have been discussed in this chapter, since upon them depend the methods used in collecting the material and labor charges, whether against the job as a whole or against any detail. The need of such detailed methods of identification will be clearer after a discussion of the principal items with which cost keeping is concerned, namely, materials, labor, and expense.