half of the object is removed
When the cutting plane extends through the object in a straight line and the front half of the object is removed, a full section is created.
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half of the object is removed |
Comparing Traditional Orthographic Views to Sectional Views
In a conventional orthographic projection, the hidden
lines in the right view show the interior detail poorly.
Replacing the right view with a full section view
does a better job of illustrating interior detail.
All the rules pertaining to alignment of orthographic views also apply to sectional views. If you look at the right orthographic and sectional views, you will notice that they are identical in shape. The only difference is that the hidden lines (in the orthographic version) become object lines (in the sectional). Remember that you are removing half of the object. When you do this, the interior detail becomes visible and hence the object lines are used.
You will notice letters and a section label on the following drawing.
Normally, it is not necessary to include these labels on a drawing containing only one sectional view. On drawings containing two or more sections, two identical letters are placed behind the arrowhead. In addition, sectional-view labels (containing the identification letters) are inserted directly below the view.
Just one more note regarding cutting plane lines. The cutting plane line can be omitted when it corresponds to the center line of the part and it is obvious where the cutting plane lies. The cutting plane line illustrated below is a perfectly acceptable alternative to the one illustrated above.
The cutting plane line can be omitted when
it corresponds to the center line of a part.
If you choose to use existing center lines instead of a cutting plane line, you should leave a gap between cutting plane arrow and the center lines (see below).
Drawings Containing Two or More Sections
Consider the following object:
Drawing the object using only orthographic views yields fairly cryptic results.
On the other hand, if we were to cut the object in two strategic locations (cut lines A-A and B-B ), we could generate more useful full sectional views.
Full sections in place of orthographic views makes the object easier to visualize. Study the section views carefully. Note that there is still hidden detail that needs to be illustrated on the sectional views.
Because this drawing contains two sections, section labels must be added.