R

Figure 8.3 shows three typical cases of cross hatching. Note that the hatching lines are equally spaced and drawn at an angle of 45° to the principal centre line in each example.

Figure 8.3 shows three typical cases of cross hatching. Note that the hatching lines are equally spaced and drawn at an angle of 45° to the principal centre line in each example.

A bush is shown in Fig. 8.4 in a housing. There are two adjacent parts and each is cross hatched in opposite directions. It is customary to reduce the pitch between hatching lines for the smaller part.

Plan A

Plan A

If the interior of a component is of an intricate nature Fig. 8.5 or it contains several parts to form an assembly, then the customary orthographic drawing would contain a confusion of dotted lines, which, in addition to being difficult to draw could also be terribly difficult to understand. The reader of any engineering drawing should be able to obtain only one positive interpretation of the component, or the draughtsman has failed in his duty. Sectional drawings are prepared which cut away a portion of the component to reveal internal details and certain standard conventions have been established Fig. 8.6 to cover this aspect of drawing practice.

Figure 8.5 shows some advantages of drawing a sectional view with a small cast component.

Note, that in Plan (A), the sectional plan gives clearly the exact outline along the horizontal axis where the casting has assumed to have been cut. This contrasts with the confusion in Plan (B) which obviously results from attempting to include all the detail by inserting the appropriate dotted lines.

Where the location of a single cutting plane is obvious, no indication of its position or identification is required. Figure 8.6 gives a typical example.

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