an elliptical edge. To make an isometric drawingof this block, draw the circumscribing rectangleon the top multi-view view, lay off equalintervals as shown, and draw perpendiculars atthese intervals from the upper horizontal edge ofthe rectangle to the ellipse. Then draw therectangle in isometric, as shown below, and plota series of points along the elliptical edge bylaying off the same perpendiculars shown in thetop multi-view view. Draw the line of the ellipsethrough these points with a french curve.Alternate Positions of Isometric Axis.— Upto this point, the isometric axis has beenused with the lower leg vertical. The axismay, however, be used in any position, pro-vided the angle between adjacent legs is always120 degrees. Figure 5-44 shows how varying theposition of the axis varies the view of the object.Diagonal Hatching in Isometric.— Diagonalhatching on a sectional surface shown in isometricshould have the appearance of making a 45-degreeangle with the horizontal or vertical axis of thesurface. If the surface is an isometric surface (onethat makes an angle of 35°16’ with the plane ofprojection), lines drawn at an angle of 60 degreesto the horizontal margin of the paper, as shownin figure 5-45, present the required appearance.To show diagonal hatching on a non-isometricsurface, you must experiment to determine theangle that presents the required appearance.DIMETRIC AND TRIMETRIC PROJEC-TION.— TWO other subclassifications of theFigure 5-45.-An example of diagonal hatching in isometric.axonometric projection category are dimetric andtrimetric projections; however, these types are usedless frequently than isometric projections and willnot be discussed further in this training manual.OBLIQUE SINGLE-PLANEPROJECTIONWe have seen that an object may be drawnshowing length and width on a single plane. DepthFigure 5-44.-Various positions of isometric axes.5-24
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