Figure 5. The figure 5 should start at the point 1 and extend downwards one-third of the total height. The lower part of the figure should then be drawn, being tangent at point 3 and 4 and slightly curled up at 5 where it should extend a little further to the left of the upper part. The horizontal part 1-2. should not extend quite up to the right-hand side of the circumscribed parallelogram.
In all cases where inch or foot sizes are employed, they should be made clearly and regularly and should be not less than one twentieth of an inch in length.
Letters and figures should always be made by beginners by first preparing guide lines drawn with a pencil. Even in case the guide lines have been drawn upon the detailed paper, it is also advisable to draw them upon the tracing cloth, or place under the cloth a sheet similar to Fig. 34, with the lines drawn in ink, to act as a guide. This practice should be continued until enough skill has been acquired to make the letters uniform, without the assistance of more than a line or two.
The only manner in which a person can become proficient in lettering is through practice. A piece of paper ruled up and having the slant of the letter placed upon it as shown in Fig. 34 will be found an excellent thing on which to practice lettering. Letters can not be made nicely and quickly as one would suppose. Care and time are required until the draftsman becomes proficient in this respect.
Abbreviations. In the making of drawings certain abbrevia tions are used in order to save time and for the sake of convenience in many other respects. These abbreviations together with what they signify are given in Table IV. They should be carefully studied and should be written close to the material to which they apply and should at least be one-sixth to one-eighth of an inch from the material. Never write dimensions or letters so close to a line that they will interfere with the line. In writing dimensions at a con siderable distance from the piece of material or place to which they apply, an arrow is used to indicate their proper position. In all such cases the arrow head should be at the end of the line which points to the place to which the abbreviation or dimension applies.
Fig. 35 illustrates some cases and also shows the form which the arrow should take in order to present a good appearance on the drawing.
Dimension and Material No= tation. Proper Placing. A ing may be said to have been correctly dimensioned when any desired necessary dimensions may be obtained from it without it being required that any sions should be added or tracted or divided in order to obtain the desired result, and when no unnecessary dimensions are upon the drawing. By essary dimensions are meant those dimensions which are required in order that the material may be fabricated so that the finished struc ture is as desired. Dimension lines should be full, not dotted or dashed; guide lines, which are lines indicating the limits of the dimensions, should not extend beyond the dimension line. The dimensions should be placed where possible above the line and should not, as mentioned before, touch the line at any place. Dimension lines should be far enough from the piece which they dimension in order that the letters and figures indicating the character of the material and its size may be placed between the dimension line and the material itself. Fig. 36a shows good practice and Fig. 3Gb poor practice.
Arrow heads are a source of trouble and should be made with care if the drawing is to present a good appearance when finished. They should be made as indicated in Fig. 36a and Fig. 36c, and not as in Figs. 3Gb and 36d. They should not consist as indicated in the figure showing the wrong construction, of a cross or half cross of a straight or nearly straight line, but should have a gradual slope as in Fig. 37 where it is greatly exaggerated.
Dimensions as mentioned above should be placed above the dimension line where possible and the material should be noted so as not to interfere with the dimensioning. Figs. 3Sa and 3Sb show good practice and Figs. 3Sc and 3Sd poor practice. Sometimes it is necessary to place the dimensions as in Fig. 3Sc and 3Sd but never place the material notation as shown in the same figures. Fig. 38b gives the preferable method.
When several spaces are equal, the matter may be written as so many spaces at so much is equal to so much, or each space may be dimensioned separately as shown in Figs. 3Sa and 3Sb. In case the space is too small to write a single dimension in it clearly, the dimension may be put at one side and an arrow used to show where it belongs, Fig. 35.