A full section (or cross section) is a view of an object which is imagined to be cut entirely in half, with half of the object then removed so that the cut surface can be viewed for its details. However, the imagined removed part is not left out of the other views.

The cut surface is represented by section lines. Different materials can be represented by various arrange­ments of these lines but, for the most part, regular section lining is used and a note is added to specify the material.

The extent of the cut surface, also called the cutting plane, is shown by a cutting plane line located on one of the principal views. This line indicates the direction from which the principal view is to be viewed to derive the section. In addition, the line indicates where the section is located with relation to the principal view. Note that the cutting plane line is composed of long dashes alternating with a pair of short dashes.

FIGURE 8.1 ■ Front view and full section.

Figure 8.1 illustrates a full section using regular section lining. Note the position and extent of the section in relation to the cutting plane line.

FIGURE 8.2 ■ Front view with two full sections.

A print may show several different sections of the same part when one sec­tion does not adequately show the inte­rior details. However, the sections shown may not be full sections, but rather may be sections that represent only portions of the part. How these sections are derived is indicated by as many cutting plane lines as there are sections needed to show the interior of the part. Each section is identi­fied by pairs of letters that are the same as those located near the points of the cutting plane line.

Figure 8.2 illustrates two full sections of a part. Note how each section is iden­tified with relation to the cutting plane line. Section lines are shown only where the imaginary cut has passed through the material. Their arrangement shows that the part is made from one piece of mate­rial. It is preferred practice not to show broken lines on section drawings. How­ever, they are sometimes included to help interpret the shape of the part.






FIGURE 8.3 ■ Front view and half section view.


A half section is a view of an object which is imagined to be cut only halfway through (a one-quarter section of the part, Figure 8.3). The cut portion is then removed so that the details of the cut surface can be viewed. The view of the cut surface shows one half as a section and the other half as it normally appears in a principal view. Half sections are used primarily to show the interior construction details of symmetrical parts.

Section lines are used to indicate the imaginary cut surface of a half section in the same manner as for full sections. The cutting plane lines serve the same function as those used for full sections, but differ as shown in Figure 8.3. Note the difference in the way a half section is represented as compared to a full section.

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