In the preliminary operation of producing a regular mechanical or instrumental drawing, it is necessary to make a “sketch,” in pencil, of the object to be represented. The American Machinist has given in a few words the order to be followed, in effecting the best results; we quote, as follows:
“In making a free-hand sketch of an object from the model it is well to observe the following order: Look the model over carefully and determine the number of views necessary to illustrate it fully, drawing the same, free-hand, in their proper relation to each other, on sketching paper. Look the sketch over carefully to see that nothing has been omitted, and put on dimension lines, after which scale the model carefully and put on dimensions. Do not put in the dimensions at the same time the dimension lines are drawn; have all the dimension lines in place before attempting to insert dimensions.
“Follow the same order in making the drawing with instruments as was used in making the sketch; that is, draw the views in their proper relation to each other, put in dimension lines, then dimensions, and lastly notes and title. If section drawing is made, do not draw section lines in pencil.”
POINTS TO BE OBSERVED IN SKETCHING.
1. Especial attention is to be paid to outlines—edges of plane surfaces are lines; when a line is made it represents the edge or outside of something.
2. Learn to be accurate before being rapid.
3. A sketch should be intelligible to any one, even if they are unacquainted with drawing.
4. Horizontal and vertical lines and a few curves will enable one to make almost any simple sketch.
5. It must be also remembered in making drawings from actual measurement that the instruments are not in the first place employed; the rough sketch is first made and then it is converted into a drawing. The draughtsman makes a rough sketch entirely by the hand and eye, measures the various parts, and jots down the measurements in his sketch; after this he reduces the whole to the desired scale, and proceeds to make his mechanical drawing.
6. Let the sketch book be the constant companion of the student; it may be advantageously filled with outlines of machine or other work suitable for preservation, to be made into finished drawings, or for reference. Sketches are often valuable for reference as aids in originating new designs.