Returns include all statements which give the re sults of operations or the records of material used, whether for direct product or for supplies; also rec ords of time expended and wages paid. Returns may also include, all summarized reports and similar documents. These returns have their origin where the work is being done and where material is being drawn from stores and worked into finished product. It may assist in the visualizing of these matters if re turns are considered as moving upward from the points where the actual operations are performed, being constantly consolidated into briefer statements till they are merged into the general books and gen eral consolidated reports. Figure 12 (page 125) shows a typical work card on which may be recorded the amount of time expended on any given operation and the rate of pay which the operator is to receive. This card bears the order number or letter which has been assigned to this particular operation and piece of work and is, therefore, a basic factor in cost find ing, whether it refers to a lot of machines or a minute detail of any one of them.
9. Necessity of identifying work.—If costs are to be obtained, whether of large lots of machines, a single machine, or of each part of a machine, some means must be provided for identifying the lot or machine or part. No two machines or parts may bear the same distinguishing mark, and if many thousands of pieces are passing thru the works at any one time it is obvious that some system must be adopted that will be capable of great expansion without danger of repetition. Furthermore, constant reference must be made to the several departments of the factory. To write the names of these departments out in full would take too long .and would be a waste of labor. It is customary, therefore, to refer to departments by number or symbol. Again, in making up shop orders it is necessary to specify the operations, or sequence of operations, on each piece. This also may involve reference to tools and equipment. In a large works the tools and equipment may be many and diverse, including many special jigs, fixtures and similar apparatus; the number and character of the operations performed may also be many and varied. Furthermore, the materials , used may be of many kinds and, since constant reference must be made to them, they also should be the subject of abbreviated nomenclature. With the constant and rapid growth of the methods of planning all operations in advance, as advocated by modern production engineers, these last items assume great importance in factory admin istration. The more accurately all machines, opera tions and materials are identified, the more accurately and easily can productive costs be allocated. The laying out of a good system of identification is, there fore, a necessity, whether viewed from the standpoint of operating administration or of cost finding.
10. Mnemonic symbols.—There are several identi fication methods now in use. In many places the de partments are known and referred to by simple letters, such as A, B, C, D. Where only a few departments are to be handled this method is adequate. If the departments are numerous, and it is desired to apply numerical identification to other lines, a system of mnemonic symbols is often employed. Thus the let ters rr A might be used to indicate the transformer assembly department, the letters s M might indicate the screw machine department, and so on. Simi lar abbreviations are commonly employed to indicate the materials used. Thus c i indicates that the part
is cast iron; 3.1 s, that it is of machine steel.
The problem of identifying operations is a little more complex. If only a few operations are in use, mnemonic symbols are adequate and are often used. Thus TN may signify turn, BO may mean bore, GE may signify grind, and so on, each enterprise com piling symbols suited to its own operations. Some times the use of symbols is obviated by printing all the operations on the side of the cards which give in structions or record returns, as illustrated on the work card, Figure 14 (page 130), in such a manner that the facts may be indicated by a check mark. This method also saves writing, but its use is limited to in dustries involving standard operations.
The problem of identifying departments or opera tions is, in general, an easy one compared to that of identifying the products and parts of products, par ticularly in large plants doing a wide range of work. In factories which make large products, such as steam engines, and where a comparatively small number of machines are being produced at any one time, mne monic methods are sometimes used. Thus, in some shops of this character the term "Osp" might be used to designate all drawings for an engine built for a certain hospital, and each drawing might bear this symbol followed by a serial number which would locate the drawing in the series belonging to that engine, the drawing serving as a basis for production orders and cost charges.
11. Drawing numbers.—In large factories with a variety of products, however, these simple methods of identifying machines and machine parts fail com pletely, and identification must usually rest upon a carefully arranged system of drawing numbers, so called. In a very large works where many thousands of drawings are made yearly, this necessitates a care ful consideration of the entire manufacturing prob lem, and perhaps the separation of the product into distinct classes. Here mnemonic or, in fact any, sys tem of symbols based entirely on letters is usually in adequate or too cumbersome, and numbers, or com binations of numbers and letters, are used. Thus the symbol K 24,689 might, in such a system, identify the drawing of a steam-engine cylinder, the letter indi cating the class of product, and the numerical part indicating its place in the series. Sometimes, again, all drawings are numbered serially and an index is kept which shows the serial numbers of the draw ings used for each machine. The drawing of any part may be found by looking at the index of the drawings that were used in making the machine and finding the serial number of the particular drawing on which the part would be found. Sometimes, too, a numbering system based on the Dewey decimal system of classification is used, certain classes of num bers being set aside for certain blocks of machines or product. Thus, all numbers beginning with .012 might indicate transformers and all numbers begin ning with .013 might indicate oil switches. In practice the decimal point is omitted for convenience, and the integers in the number are always preceded by a cipher. The Dewey system has the advantage of unlimited ex pansibility without repetition; it can be made as com prehensive as may be desired, and hence is well suited for large works. The system that is best for one shop may not apply to others. however, and each case re quires special study in order that the system may be made comprehensive without being cumbersome.