To transfer an angular dimensional view from an orthographic view to an isometric drawing, convert the angular dimensional value to its component linear value and transfer the component values directly to the axis of the isometric drawing. Figure 41 (on the previous page) illustrates this procedure by showing two angular dimensions that have, been converted to their respective linear values, then showing how these values are transferred to the isometric axis. Normally, a draftsman simply measures his full-sized orthographic views and then transfers the information. If the information is not available, they make a supplementary layout from which the necessary values may be measured. Supplementary layouts may be made on any extra available piece of paper and should be saved for reference during the checking of the drawing.
Figure 42 (on the following page) is the solution to the problem in figure 40 and was derived by the following procedures:
Step 1. To the best of your ability, make a freehand sketch of the solution (view A).
Step 2. Using very light lines, lay out a rectangular box whose height, width, and length correspond to the height, width, and length given in the orthographic view (view B).
Step 3. Using very light lines, lay out the specific details of the object. Where necessary, make supplementary layouts that furnish the linear component values which can transfer to the isometric axis. In this case, the 30° component layout is shown in figure 41 (on the previous page).
Step 4. Erase all excess lines and smudges, check your work, then draw in all lines to their proper color and pattern.
c. Holes in Isometric Drawings. There are two basic methods for drawing holes in isometric drawings. One method is to use instruments and draw the holes by using the four-center ellipse
method. The other method is to use an isometric hole template as a guide. The template is much easier and faster to use, but templates are available only in standard hole sizes. Very large or odd-sized holes may only be drawn by using the four-center ellipse method.
The four-center ellipse method is presented in figure 43 (on the following page). When you use this method, be careful that the four centers are located accurately. If the centers are not located properly, the four individual arcs will not meet to form a smooth, continuous ellipse. A good practice that will help you draw a smooth, continuous ellipse is to lightly construct the ellipse, then check it for accuracy before drawing in the final heavy arcs.
Was this article helpful?