ABSTRACT
Drawings provide a clear and concise method of conveying information to individuals and other departments. Original drawings were stored on microfilm by photographically reducing them on to film which was then mounted and suitably filed. When required they were re-enlarged and printed. The two common methods used to represent a three-dimensional object on a flat piece of paper are orthographic projection and pictorial projection. A part with little internal detail can be satisfactorily represented by orthographic projection. Two kinds of pictorial projection are used: isometric projection and oblique projection. British Standards sets out to standardise conventions used in engineering drawings which include: layout, lines, systems of projection, sections, conventional representation and dimensions. In the part is dimensioned from the datum in sequence, i.e., cumulatively, known as chain dimensioning. Difficulties also arise if a part is dimensioned from more than one datum.
