Regardless of the system used, the leader lines must be drawn in the same isometric plane as the surface they are defining. The guidelines for the dimensions in the aligned system are drawn parallel to the edge being defined, while the guidelines for the unidirectional system are always horizontal. Figure 53 (on the previous page) is another example of the unidirectional system. The numbers are drawn either 1/8 or 3/16 inch in height in both systems.
f. Isometric Sectional Views. Isometric sectional views are used for the same reasons that orthographic sectional views are used, to clarify objects by exposing important internal surfaces that would otherwise be hidden from direct view. Figure 54 shows a full isometric sectional view and a half isometric sectional view. Note that, as with orthographic sectional views, hidden lines are omitted and the cross-hatching lines are drawn medium to light in color, 3/32 apart at an inclined angle. Isometric sectional views do not require a defining cutting plane and are usually presented as individual pictures with no accompanying reference drawing. Dimensions are placed on an isometric sectional view in the same way they are for regular isometric drawings.
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