You can, of course, make a perfectly usable drawing with a felt pen or a piece of chalk. At the other extreme you may have seen drawings being produced on most elaborate draughting machines coupled to electronic display units. So, a few words on the types of drawing before dealing with how to make them.
I will start with the sketch. This is used for three main purposes.
(1) To record an idea so that it is not forgotten later.
(2) To record the measurements or shape of an existing piece of machinery.
(3) To transfer information from (e.g.) a large drawing to the workplace - lathe or bench - where use of the drawing would be inconvenient.
Most readers will have had the experience of forgetting A sketch need only be very simple, just the bare bones, and needs no elaborate equipment. The back of an envelope is, however, unwise, as if it drops wrong way up it may get thrown away. Professional engineers keep an ideas book for them, much wiser, and I show in Fig. 62 one taken from "The Life of Nasmyth"
by Smiles showing the first sketch of his steam hammer. There is some suspicion that the 'almost to scale' drawing of the complete hammer, bottom left, was done later, but you will see that he has not only sketched the arrangement on the other view, but also worked out the essentials in figures, too. Incidentally, Nasmyth used both pen and pencil for these sketches, and you can see that he was a good draughtsman.
To illustrate the second type I show Fig. 63 taken from one of my own books. This is what I call a hand sketch. No instruments are used, but as I use sectional books -ones which have the pages of squared paper - it is possible to show the component in its proper proportions, though not, of course, exactly to scale. A sketch of this type is usually done at leisure and with care, as a missed dimension could be serious. The paper is of very good quality to withstand erasure, and I use a sharp H grade pencil, sometimes lining in later. (This sketch was made over 40 years ago, and has worn well).
The third type of sketch is the most common, especially among jobbing yj&Ur.'iinytitjU- SiymwM^pli' -* i^W/n— «-7 «fawn u-4.ti.tue
workers and model engineers. In a confined workshop it is often difficult to find space for a large drawing (but, as we shall see later, most firms have now abandoned their use anyway) and if you are working from a book or a magazine it is unwise to have it within range of a suds pump. So, we make a sketch of the part and take this to the workplace. The procedure also enables us
Was this article helpful?