About the hidden part of an object

1. ADAMA SCIENCE AND TECHNOLOGY UNIVERSITY
SCHOOL OF MECHANICAL, CHEMICAL AND MATERIAL
ENGINEERING
DEPARTMENT OF MECHANICAL ENGINEERING
ENGINEERING DRAWING ; MEng1102
CHAPTER-6
SECTIONAL VIEWS
Date, Jun 2024
05/07/25

2. Learning Outcomes
At the end of the lesson the students will be
able to:
•Define Sections and Identify the Necessity of
sectional views
•List the types of sectioning and differentiate
between them
•Practice the convention in sectioning
•Make practical exercise on both sectional view and
pictorial section.

3. 6.1. Introduction
 Sections are used to clarify the interior construction
of a part that can not be clearly described by hidden
lines in exterior views.
 By taking an imaginary cut through the object and
removing a portion, the inside features may be seen
more clearly.

4. 6.2.Necessity of sectional views
 To see clearly interior features of the object.
 To clarify the interior details of an object that can
not be clearly described by hidden lines.
 To reduce confusion.

5. 6.3.Terminology & common practices
Basic Terminologies in sectional views
 Cutting Plane
 Cutting Plane Line
 Section Lines

6. Cutting
plane
CUTTING PLANE
Cutting plane line
 Cutting plane is a plane that imaginarily cuts
the object to reveal the internal features.
Section lines

7.  Cutting plane line is an edge view of the
cutting plane.
CUTTING PLANE LINE
Indicate the path
of cutting plane.

8. ANSI
standard
Thick line
Thick line
JIS & ISO
standard
Thin line
CUTTING PLANE LINESTYLES
Viewing
direction
Viewing
direction
Viewing
direction

9. SECTION LINING
 Section lines or cross-hatch lines are used to
indicate the surfaces that are cut by the cutting
plane.
Section
lines
Drawn with 4H pencil.

11. SECTION LINES SYMBOLS
The section lines are different for each of
material’s type.
Cast iron,
Malleable iron
Steel Concrete Sand Wood
For practical purpose, the cast iron symbol is
used most often for any materials.

12. SECTION LINING PRACTICE
The spaces between lines may vary from 1.5 mm
for small sections to 3 mm for large sections.
COMMON MISTAKE

13. SECTION LINING PRACTICE
It should not be drawn parallel or perpendicular
to contour of the view.
COMMON MISTAKE

14. 6.4.KIND OF SECTIONS
1. Full section
2. Offset section
3. Half section
4. Broken-out section
5. Revolved section (aligned section)
6. Removed section (detailed section)

15. FULL SECTION VIEW
The view is made by passing the straight cutting
plane completely through the part.

16. OFFSET SECTION VIEW
The view is made by passing the bended cutting
plane completely through the part.
Do not show the edge views
of the cutting plane.

17. TREATMENT OF HIDDEN LINES
Hidden lines are normally omitted from section
views.

18. HALF SECTION VIEW
The view is made by passing the cutting plane halfway
through an object and remove a quarter of it.

19. HALF SECTION VIEW
A center line is used to separate the sectioned half
from the unsectioned half of the view.
Hidden line is omitted in unsection half of the view.

20. The view is made by passing the cutting plane normal
to the viewing direction and removing the portion of an
object in front of it.
BROKEN-OUT SECTION VIEW

21. A break line is used to separate
the sectioned portion from the
unsectioned portion of the view.
BROKEN-OUT SECTION VIEW
There is no cutting plane line.
Break line is a thin continuous
line (4H) and is drawn freehand.

22. EXAMPLE : Comparison among several section techniques

23. Revolved sections show cross-sectional
features of a part.
No need for additional orthographic views.
This section is especially helpful when a
cross-section varies.
REVOLVED SECTION VIEW

24. REVOLVED SECTION VIEW
Basic concept

25. REVOLVED SECTION VIEW
Basic concept

26. Given
Step 1
a. Assign position of cutting plane.
b. Draw axis of rotation in front view.
Steps in construction
REVOLVED SECTION VIEW
Edge view of
Edge view of
cross-section
cross-section

27. Steps in construction
Given
a. Transfer the depth dimension to
the front view.
REVOLVED SECTION VIEW
Step 2

28. Steps in construction
Given
REVOLVED SECTION VIEW
a. Draw the revolved section.
Step 3
b. Add section lines.

29. Steps in construction
Given
REVOLVED SECTION VIEW
FINAL PICTURE

30. Placement of revolved section
1. Superimposed to orthographic view.
Superimposed
Break
2. Break from orthographic view.
REVOLVED SECTION VIEW

31. 6. Removed section
Removed section is revolved section.
Used where space does not enough for
revolved section
Can be located elsewhere on a drawing
with properly labeled
REMOVED SECTION VIEW
Section view is shown outside the view.

32. Example : Revolved vs. removed sections.
Revolved section Removed section
REMOVED SECTION VIEW

33. 6.5.CONVENTIONAL PRACTICE
Omit the section lines on the section view of
 Rib
 Web
 Lug if the cutting plane is
passed flatwise through.
 Spoke, if the cutting plane is passed
longwise
through.

34. Rib and Web are thin, flat feature of an
object that acts as a structural support.
Rib Rib
Web

35. Rim
Spoke is the rod radiating from the hub to the
rim of a wheel.
Spoke
Spoke
Rim
Hub
Hub

36. Lug is an ear which is built as portion of an
object for attachment.

37. EXAMPLE : RIB
Normal multiview drawing
Normal section view
Section view drawing with
convention

38. EXAMPLE : WEB : flatwise cut
Normal multiview drawing
Normal section view
Section view drawing with
convention

39. EXAMPLE : WEB : crosswise cut

40. EXAMPLE : SPOKE
Misleading impression

41. EXAMPLE : LUG

42. 6.6. Aligned Section
Aligned section is a section view that is drawn
by imaginary rotating the object’s features
appeared in a principal view about symmetry
Axis.

43. Example : Hole
Gives the impression that this
holes are at unsymmetrical

44. Example : Hole

45. Example : Rib

46. Example : Ribs & Holes

47. Example : Lug

48. END