An introdction to Sectional View

1. 5. Sectional View
Complied By: Habtamu Geremew
Email: habti.geremew@gmail.com
Engineering Drawing.
Gondar institute of
Technology

2. Sectional view
There are objects with complicated interior details
and when represented by hidden lines, may not
effectively reveal the true interior details in MVD.
A sectional view is obtained by imagining the object, as
if cut by a cutting plane and the portion between the
observer and the section plane being removed.
The cut line is called a “cutting plane”, and can be done
in several ways.

3. Visualizing the Cutting Plane and cutting plane line
To draw a sectional view, imagine that a wide-blade knife has cut
through the object. Call this knife a cutting plane.

4. Cutting Plane lines have two forms:
A thick hidden (evenly spaced dashed) line.
A phantom line in accordance with ASME Y14.2M.
The arrows on the cutting-plane line indicate the direction
of sight when looking at the section view.

5. 1. Full Section
A full section is a sectional view that shows an object as if it were cut
completely apart from one end or side to the other.
Normally a view is replaced with the full section view.
The section-lined areas are those portions that have been in actual
contact with the cutting-plane.

6. Replacing the normal view by sectional

7.  The two most common types of full sections
are vertical sections, in which the front view
is sectioned and profile sections, in which the
side is sectioned.

8. 2. Half Section
Half Section is used to the exterior and interior of
the part in the same view.
The cutting-plane line cuts halfway through the part
and removes one quarter of the material.
The line that separates the different types (interior
and exterior) may be a centerline or a visible line.
Half sections are commonly used on symmetrical
objects.

9. Half section

10. 3. Offset Sections
Used to show parts and features that do not line up with each other.
Cutting-plane line does not travel in a straight line.
The versatility of this section makes it very useful.

11. 4. Aligned Sections
Aligned sections are used when a feature is out of alignment
with the center plane.
An offset section would distort the image.
Usually used on symmetrical circular parts.
All parts and details are rotated into the section view.

12. 5. Revolved Sections
Show a cross-section of an area turned 90 degrees to the object.
Put into a drawing to show an area not normally shown.

13. 6. Removed Sections
A removed section is a section that is not direct projection
from the view containing the cutting plane – it is located
somewhere else in the drawing.

14. 7. Broken-out Sections
A broken-out section shows an object as it would look if a
portion of it were cut partly away from the rest by a
cutting-plane and then “broken off” to reveal the cut
surface and insides.
Uses short break line.
Used to generate a section for a small area without using a
cutting-plane line.
Used to enhance the orthographic view by giving the viewer
a better look at key interior details.

15. Broken-out Section

16. A. Sectioning Shafts
Used to show a break in a longer part allowing better used of drawing surface.
Gives the impression of a 3-D break on the shaft.

17. B. Assembly Sections
Shows how parts fit together
Allows better clarity with a complicated assembly of parts.
Shows how parts not only fit together, but allows for a
visual view of how they function.

19. C. Section Lining
Materials – Common materials
The symbol for cast iron can be used for most section
views.
45 degree angle lines should be used.
1/8” between lines.
All lines should be uniformly spaced
Thin sections may be blackened in completely
Avoid section lines placed at angles greater than 75° or
less than 15° from horizontal.
Section lines are NEVER drawn parallel to or at right
angles to visible lines.
Section lines should not cross object lines.
If the drawing shows more than one piece in section,
draw the section lines at different angles.

20. Continued

21. Section lining/continued

22. Section Lining – Line Placement
If the outline of the object has 45 degree lines, 30 or 60
degree lines should be used.
Assemblies with several parts should be lined with varying
angle section lines.

23. D. Special Cases
Certain exceptions are made to the general sectioning rules
for:
Ribs and Webs in Section.
Hidden and Visible Lines.
Alternate Section Lining.
Certain Parts usually not sectioned.
Rotated Features in Section.

24. Ribs and Webs in Section
Show ribs as if the cutting plane passed in front of the rib.

25. Ribs and Webs in Section
Flat part, at right angles to the flat side, Show the section lines for
that part.

26. Hidden and Visible Lines
Do not draw hidden lines on sectional views unless they are needed.
Include all lines that would be visible on or beyond the plane of the section.

27. Alternate Section Lining
Alternate section lining is a pattern
made by leaving out every other
section line.
Alternate section lines are useful to
show ribs and other thin, flat pieces
in one-view drawings.

28. Other Parts NOT Sectioned
Do not draw section lines on
spokes, shafts, bolts, pins, rivets
and gear teeth when the cutting
plane passes through them.
Draw section lines when cut
across the axis

30. Th a n k You
Ver y M uc h
Comment/questionsession
So now what are you
going to do?
Department of Mechanical Engineering

31. Exercise session