The principle title of a drawing should contain at least seven items: (1) name of principal details shown; (2) name of machine; (3) firm name and location; (4) scale of drawing; (5) date of completion; (6) draftsman's signature; (7) filing number.
To these are often added others, but for purposes of filing and reference the above at least must be put on. The filing number may or may not be put in the title frame, but it is really a part of it. It is often put in the margin below the title.
An arrangement of title should be established and then followed exactly, without variation either as to location on sheet or detail make-up. Abbreviated words are always permissible in titles, provided the meaning is clear. Special care must be taken in punctuation, however, as a title, whether abbreviated or not, has an unfinished appearance if the periods, commas, and other necessary punctuation marks are not included.
The sample title illustrated in Fig. 123 indicates the arrangement chosen for the drawings of Part I. Note that in this special case the residence of the student draftsman ha3 been substituted for the file number of the drawing.
Fig. 122. Sample Titles Showing Effect of Non-Uniformity of Lettering.
Fig. 123. Sample P1ate Title Properly Drawn.
This style of title must be put with care on every drawing, even on the rough pencil layouts. In the latter case it may of course be left in pencil, as the rough layouts are not to be inked.
Both bond paper and tracing cloth are used in business practice for finished drawings. It is desirable to keep a stock of both in any drawing office, so that either may be used as occasion requires. Bond paper stretched on the board gives a beautiful surface to take the ink, and very handsome and effective detail or assembled drawings can thus be produced.
Changes are not quite as readily made on bond paper as on tracing cloth, and it takes a little longer to make the blue print. In other ways the bond paper is not quite as flexible to use as the tracing cloth. However, one must be guided entirely by shop conditions to settle the question of preference. As the tracing cloth is generally used, and suits the purpose of the student better, it will be required in this work.
The inking should be done on the rough side of the cloth. One reason for choosing this side is that as the cloth tends to curl under toward the glazed side, the drawing as it lies right side up will tend to straighten itself. This seems to be a small point, but it is a very important advantage for filing and for the convenience of those who are to handle the drawings. Also the rough side takes colors and inks better than the glazed side. To trace on the glazed side is not wrong, for it is often done, but it possesses no advantages of its own, and has the disadvantage mentioned above.
Chalk dust scattered over the surface of the cloth after it is tacked down will remove the slightly greasy coating which prevents the ink from flowing well from the pen. This is always necessary if the glazed side be used, and usually for the rough side. The chalk must be carefully removed from the cloth before inking.
The first step in inking is to draw the center lines. Remember that accurate intersections are of the utmost importance. No circle is complete without two intersecting lines, preferably at 90 degrees, to determine its center, and these lines should be inked before the circle. When this is done, a definite point exists for the needle point of the compasses. If the circle is drawn first, the needle point may not be placed accurately at the center on the pencil drawing beneath, thus throwing the location out.
Likewise the principal center lines of pieces, the lines around which the pencil drawing was built up, should be at once put in.
The main body of the drawing, the full lines, should be taken next. In general, circles and arcs should be inked first, but there are cases where it is easier to run the arcs into the straight lines than to match the straight lines to the arcs. These are exceptions, however, and can be judged only as the case arises.
Straight lines, horizontal and vertical, should be inked with the T-square and triangle in position. It is a common practice to dispense with the use of the T-square entirely in inking in, using the triangle to match the lines to the arcs already drawn. A necessity for this implies very poor work on the arcs, for with any reasonable care true horizontal and vertical lines will match the arcs all right. With regard to time required, the accuracy with which the T-square may be brought up to a line, or the triangle set on the T-square, more than makes up for the time gained in even an approximate setting of the triangle without a guide. It is just as easy to cultivate the habit of holding the T-square and triangle with the left hand and the pen with the right, and draw an exact line, as to lapse into the other method, which is not workmanlike.
The lines of the body of the drawing depend for their width upon the size of the detail. For a large piece they may be 1/32 inch wide, and the shade lines 3/64 inch. For a small detail such widths would be too great. Remember that contrast is the principal aim, and to produce it is the only reason why we use different kinds of lines on a drawing. Hence the greatest care must be exercised to prevent body lines from becoming confused with center or dimension lines, and vice versa. Also thick lines are desirable for the production of a bold blue print.
Shade lines certainly improve the drawing from an artistic standpoint, and the student has been shown in Machine Drawing, Part I, how to put them on when desired. Whether or not it is desirable to adopt them on all working drawings is not the purpose of this book to decide, or even discuss. Almost always drawings can be made perfectly clear without them, and are so made and satisfactorily used in probably the majority of shops. Some shops are willing to pay for the extra time necessary to put on shade lines; this, however, is purely their own investment.
Cross-section lines are usually drawn at an angle of 45 degrees with the horizontal, and on sections which are adjacent to each other the slope should be in different directions. If three or more sections come together, the width between section lines can be so changed as to indicate clearly the different parts. An example of this is shown in Fig. 124.
The spacing of section lines must not be too fine, rarely closer than 1/16 inch, more often from 3/32 to 1/8 inch, else the labor involved is too great and uniformity practically impossible. It is a waste of time to rule in section lines on the pencil drawing; they may be sketched in freehand, as shown on the original layout of the steam cylinder. Even spacing concerns the tracing alone, and the student should train his eye to regularity as he traces. The thickness of section lines may be intermediate between that of center lines and the body lines of the drawing.