Technical drawing is an essential part of the craftsman’s professional equipment. The fact that the subject has some prominence in the syllabus of the City and Guilds should be noted by the student. A really efficient tradesman needs to be capable of “setting out,” i.e., drawing the form, construction and dimensions of any straightforward piece of work that he is called upon to undertake. The knowledge that his technical drawings may also be required to give effective guidance to others than himself should serve to impress upon the young woodworker the need for clearness and accuracy.
Working drawings are normally set out to show clearly the following aspects of the job concerned: (1) Main elevation; (2) Plan; (3) Sectional views (as required); (4) All necessary dimensions; (5) Constructional data.
SCALE AND FULL-SIZE DRAWINGS
Scale drawings. In scale drawing a selected lineal unit is made to represent a larger one. For example, in a drawing produced to a scale of 1 in. to the foot, each inch measured off on the drawing will stand for twelve inches on the actual job. A convenience of the method lies in the fact that, by first drawing out a design on a much reduced scale, it is possible to judge of its ultimate appearance and proportions before proceeding with a full size setting out. Apart from this advantage, it should be noted also that a scale drawing, accurately figured as to dimensions, is often all that is required for the guidance of a really practical man.
Questions are sometimes encountered in the City and Guilds examinations, the answers to which entail use of scale drawings. A typical test of this kind would require the student to set up a main drawing of, say, a bookcase to a given scale. Certain constructional features would perhaps need to be shown to a different scale, while the mouldings and ornament would probably be asked for in full size.
Full-size drawings. Two methods are used for the production of full-size drawings. The first is to set up the drawing upon detail paper — a thin, tough paper that is specially suitable for subsequent blue-print production.
The other method consists in setting out the job in section on a rod or skid, generally in the form of a prepared (surfaced) board 8 ins. or 9 ins. wide and of suitable length.
The paper drawing. When a paper full sizing is set up, the various views of the job are superimposed one upon another: they are made distinguishable from each other by means of different colours. Thus, the main elevation would be drawn in black, the plan in red, and sectional details blue. The advantage claimed for this method—apart from the convenience of having only one sheet of drawings—is that it ensures accuracy in setting out, due to the fact that the various sections check against each other.
Often it is sufficient to set out only half of the main elevation and plan—that is, of course, when the two halves (right hand and left hand) of a job are similar. Dimensions in such a case are taken from a clearly marked centre line. The sectional view is shown in the ordinary way.
Full-size drawing on paper is especially suitable for the representation of “feature” work, i.e., elaborate cabinet pieces and woodwork that has much carved or inlaid detail to be shown. Special veneering treatments are also most readily conveyed in this way.
Figured dimensions are to be recommended, and it should be noted that such measurements should be arranged to check against over all sizes.