Full Sectional Views

5.2.1. Information about the Full Section Representations

A full section is the imaginary division of an object by an unlimited cutting plane. It is used when the full section of an object is to be revealed (Fig. 5.11.).

Fig. 5.11. 1 Section A−A, 2 Section B−B

5.2.2. Full Sections without Marking of the Cutting Plane Line

The cutting plane need not be shown when this line is clear and subject to but one interpretation. This is the case when the cutting plane passes through the centre line (symmetry section). Marking is also not necessary when the plane of cutting is clearly identifiable from the view from which the section has been developed (Figs. 5.13. to 5.16.). This also applies to the fact when the cross−section is directly drawn into the view (Fig. 5.17.).

Fig. 5.12.

For full sections without marking the cutting plane line, there are the following possibilities: Full section (without further views) (Fig. 5.12.).

The shape of the sleeve is clearly visible even with a second view. It is cylindrical. This is indicated by the diameter sign. With this, the cutting plane line is clearly visible − it is through the centre line.

Representation in general view and full section (Fig. 5.13.).

Fig. 5.13. 1 Cutting plane line

The cutting plane line cannot be interpreted as passing through the centre of the object. Representation in general view and in two sections (Fig. 5.14.).

Fig. 5.14. 1 Cutting plane line

The cutting plane clearly passes through the central axes. Also, for the bolts represented (Fig. 5.15.). the line of the cutting plane of the two full sections is clear.

Fig. 5.15. 1 Cutting plane line

Representation in two full sections (Fig. 5.16.)

From one full section, a second can be derived. This must be represented in such a way as if the initial section was drawn in a view.

Fig. 5.16. 1 Cutting plane line

Representation of the cross−section within a view (Fig. 5.17.)

Fig. 5.17.

For ribs, spokes and the like, the cross−section can be indicated directly at the point for which it hilds (Fig. 5.18.).

Fig. 5.18.

2. Explain the rational representation of sectional views.

5.2.3. Full Section with Marking of the Cutting Plane Line by Arrowheads

When the location of the cutting plane is not clear, then it is marked.

The imagined cutting plane is drawn in the form of a dash−and−dot line which projects beyond the contour of the object (see Fig. 5.19.).

Fig. 5.19. 1 Centre

The ends of this centre line are drawn thick. An arrowhead is put on the centre of the thickened ends which point in the direction of sight. The size of these arrowheads is about 1.5 times that of the arrowheads of dimension lines in the drawing.

For full sections with marking the cutting plane by arrowheads, there are the following possibilities: Cutting plane located in a straight line

Offset cutting plane line

This is illustrated by the Figs. 5.20. to 5.22.

Fig. 5.21.

Fig. 5.22.

When using the offset cutting plane line, one sectional view covers internal shapes which are located in various planes. The change in direction of the cutting plane line is indicated by thickening the angle.

direction of sight is also here perpendicular to the cutting plane. The angle of twist is not given.

Fig. 5.23. 1 wrong

Fig. 5.24. Repetition

1. What are the reasons for marking the cutting plane line by arrowheads? 2. What are the advantages associated with the offset cutting plane line? 3. How is the offset cutting plane line marked?

5.2.4. Full Section with Marking the Cutting Plane Line by Arrowheads and Letters

When several full sections are necessary in one drawing and when misinterpretation will be possible, marking by arrowheads alone will not suffice.

The various sections are distinguished by letters. One uses capital letters of the beginning of the alphabet. Each cutting plane line receives a letter. These letters are located close by the arrowheads and their size is twice that of the dimension figures.

The letters must be written so that they can be read from below!

The letters used to identify the sections are such as Section A − A, Section B − B, etc. There are two possibilities which are shown in Figs. 5.25. to 5.27.

Fig. 5.25. a Section A−A, b Section B−B

Straight cutting plane line

In a simplified manner, one cross−section can be shown without edges behind it (e.g. Section A − A, right−hand side, Fig. 5.26.).

Fig. 5.26.

a Section A−A, b Section B−B, c Section C−C, d Section D−D Offset cutting plane line

This marking must be used when the part has several interior shapes or unsymmetrical arrangement which are not located in a straight line so that straight sections are useless.

The letters are used to identify clearly the individual sections.

The letters at the angles where the direction of the line changes are only written when they are indispensable for clarity. They are written so that they can be read from below (Fig. 5.27.).

Fig. 5.27. a Section A−A, b Section B−B

Repetition

1. When must the cutting plane line be marked in addition to the arrowheads by letters?

2. Explain the manner of marking by letters in greater detail (location, size and number of letters, designation of the sections)!