This document describes basic 2D technical drawing constructions and representations. It covers topics such as types of lines used in drawings, geometric constructions for shapes like triangles, circles, and ellipses, representing curved surfaces and features like fillets and holes, and drawing conventions for projections, sections, and details. The overall objectives are to identify the geometry that makes up basic 2D drawings and use manual drafting or CAD skills to create technical figures.

1. Basic 2D Constructions

2. Line type

4. Line standards
Name Convention Description Example
Center
lines
Thin lines made up of long
and short dashes
alternately spaced and
consistent in length
Symmetry about an axis
and location of centers
Visible
lines
Heavy unbroken lines
Indicate visible edge of an
object
Hidden
lines
Medium lines with short
evenly spaced dashes
Indicate concealed edges

5. Line standards
Name Convention Description Example
Extension
lines
Thin unbroken lines
Indicate extent of
dimensions
Dimension
lines
Thin lines terminated with
arrow heads at each end
Indicate distance measured
Leader Thin lines terminated with
arrow head or dot at one
end
Indicate a part, dimension
or other reference

6. Line standards
Name Convention Description Example
Long break
lines
Thin solid ruled lines with
freehand zig-zags
Reduce size of drawing
required to delineate object
and reduce detail
Short break
lines
Thick, solid free hand lines
Indicate a short break
Phantom
lines
Medium series of one long
dash and two short dashes
Indicate alternate position
of part, repeated detail or
datum plane

7. Line standards
Name Convention Description Example
Cutting
plane lines
Designate where an
imaginary cutting took
place
Indicate direction of sight
when a partial view is used
Section
lines
Indicate the surface in the
section view have been cut
along the cutting plane line

8. Important Types of Lines

9. Break line

10. Example

11. GEOMETRIC
CONSTRUCTION

12. OBJECTIVES
1. Identify the geometry that makes up basic 2D drawings.
2. Use board drafting or 2D CAD skills to create technical figures.
3. Describe the advantages of CAD contrasted with drawing with
manual instruments

13. GEOMETRY REVIEW
• Triangles
• Quadrilaterals
• Polygons
• Circles
• Arcs

14. BISECTING A LINE OR CIRCULAR ARC
Triangle and T-Square System
Compass system

15. BISECTING A LINE WITH TRIANGLE AND T SQUARE
From endpoints A and B, draw construction lines at 30°, 45°, or 60° with the given line.
Then, through their intersection, C, draw a line perpendicular to the given line to locate
the center D…

16. Triangles
Inclined lines can be drawn at standard angles with the 45° triangle and the
30° x 60° triangle. The triangles are transparent so that you can see the lines
of the drawing through them. A useful combination of triangles is the 30° x 60°
triangle with a long side of 10" and a 45° triangle with each side 8" long.

17. Any Angle in 15° Increments
With only a 30° x 60°
triangle and a 45°
triangle, you can draw
any angle in 15°
increments
The bottom
of the triangle in
each case is resting
on the blade of the
T-square. Twenty-four 15°
sectors are possible with just
these two triangles used
singly or in combination.

18. Protractors
For measuring or setting off angles other than those obtainable with
triangles, use a protractor.
Plastic protractors are
satisfactory for most
angular measurements
Nickel silver protractors are
available when high accuracy
is required

19. ANGLES
BISECTING AN ANGLE
TRANSFERRING AN
ANGLE

20. DRAWING A LINE PARALLEL TO A LINE
AND AT A GIVEN DISTANCE
For Curves
T-square Method

21. DRAWING A LINE THROUGH A POINT AND
PERPENDICULAR TO A LINE
When the Point Is Not on the Line When the Point Is on the Line T-square Method

22. TRIANGLES
DRAWING A TRIANGLE
WITH SIDES GIVEN
DRAWING A RIGHT
TRIANGLE WITH
HYPOTENUSE AND ONE
SIDE GIVEN

23. LAYING OUT AN ANGLE
• Tangent Method
• Sine Method
• Chord Method
Many angles can be laid out directly with the triangle or protractor.

24. DRAWING AN EQUILATERAL TRIANGLE
Alternative Method

25. DRAWING A SQUARE
You can use the AutoCAD Polygon
command to draw squares. The
Rectangle command is another quick
way to make a square in AutoCAD.
• T-square Method
• Diameters Method
• Inscribed Circle Method

26. DRAWING A REGULAR
PENTAGON
Dividers Method Geometric Method

27. DRAWING A HEXAGON
Each side of a hexagon is equal to the radius of the circumscribed circle
Use a compass
Centerline Variation
Steps

28. Drawing an Octagon
Given an inscribed circle, or distance
“across flats”, use a T-square or
straightedge and a 45° triangle to draw
the eight sides tangent to the circle.
Given a circumscribed square, (the distance
“across flats”) draw the diagonals of the
square. Then, use the corners of the square
as centers and half the diagonal as the
radius to draw arcs cutting the sides

29. FINDING THE CENTER OF A
CIRCLE
This method uses the principle that any right triangle inscribed in a circle
cuts off a semicircle.
Another method, slightly longer, is to reverse the procedure. Draw two
nonparallel chords and draw perpendicular bisectors. The intersection of the
bisectors will be the center of the circle.

30. DRAWING TANGENTS TO TWO
CIRCLES
AutoCAD software provides a
convenient object snap for
finding tangency.

31. DRAWING AN ARC TANGENT TO A LINE OR
ARC AND THROUGH A POINT
Tangents

32. DRAWING AN ARC TANGENT TO TWO
LINES AT RIGHT ANGLES
For small radii, such as 1/8R for fillets and rounds, it is not practicable
to draw complete tangency constructions. Instead, draw a 45° bisector
of the angle and locate the center of the arc by trial along this line

33. DRAWING AN ARC TANGENT TO TWO LINES AT ACUTE
OR OBTUSE ANGLES

34. DRAWING AN ARC TANGENT TO AN ARC
AND A STRAIGHT LINE

35. DRAWING AN ARC TANGENT TO TWO
ARCS

36. Drawing an Arc Tangent to Two Arcs and
Enclosing One or Both

37. DRAWING AN OGEE CURVE
Connecting Two Parallel Lines Connecting Two Nonparallel Lines

38. THE CONIC SECTIONS
The conic sections are curves produced by planes intersecting a right circular
cone.
Four types of curves are produced: the circle, ellipse, parabola, and
hyperbola, according to the position of the planes.

39. DRAWING A FOCI ELLIPSE

40. DRAWING A CONCENTRIC CIRCLE
ELLIPSE
If a circle is viewed with the line of sight perpendicular to the plane
of the circle…
…the circle will appear as a circle, in true size and shape

41. DRAWING A PARALLELOGRAM
ELLIPSE
The intersection of like-numbered lines will be points on the ellipse. Locate points in the
remaining three quadrants in a similar manner. Sketch the ellipse lightly through the points,
then darken the final ellipse with the aid of an irregular curve.

42. ELLIPSE TEMPLATES
These ellipse guides are usually designated by the ellipse angle, the
angle at which a circle is viewed to appear as an ellipse.

43. Irregular Curves
The curves are largely successive segments of geometric curves,
such as the ellipse, parabola, hyperbola, and involute.

44. DRAWING AN APPROXIMATE
ELLIPSE
For many purposes, particularly where a small ellipse is required, use the
approximate circular arc method.

45. DRAWING A PARABOLA
The curve of intersection between a right circular cone and a plane parallel
to one of its elements is a parabola.

46. DRAWING A HELIX
A helix is generated by a point moving around and along the surface of a
cylinder or cone with a uniform angular velocity about the axis, and with a
uniform linear velocity about the axis, and with a uniform velocity in the
direction of the axis

47. DRAWING AN INVOLUTE
An involute is the path of a point on a string as the string unwinds from a line,
polygon, or circle.

48. DRAWING A CYCLOID
A cycloid is generated by a point P on the circumference of a circle that
rolls along a straight line
Cycloid

49. DRAWING AN EPICYCLOID OR A
HYPOCYCLOID
Like cycloids, these curves are used to form the outlines of certain gear teeth and are therefore
of practical importance in machine design.

50. 2D DRAWING
REPRESENTATION

51. OBJECTIVES
1. Represent curved surfaces in multiview drawings
2. Show intersections and tangencies of curved and planar surfaces
3. Represent common types of holes
4. Show fillets, rounds, and runouts in a 2D drawing
5. Use partial views
6. Apply revolution conventions when necessary for clarity
7. Draw removed views and projected views
8. Show right- and left-hand parts
9. Project curved surfaces by points
10. Show and label an enlarged detail
11. Show conventional breaks

52. Common Manufactured Features
• Fillet
• Round
• Counterbore
• Countersink
• Spotface
• Boss
• Lug
• Flange
• Chamfer
• Neck
• Keyway/Keyseat
• Knurl
• Bushing

53. Conventional Representations
Standard orthographic projections
don’t always show complex shapes as
clearly and simply as you may wish,
so certain alternative practices,
referred to as conventions, are
accepted.
Conventions are like rules for breaking
the rules. Note how these views are
projected
Orthographic Views of Intersecting
and Tangent Surfaces.
(Lockhart, Shawna D.; Johnson, Cindy M., Engineering Design
Communication: Conveying DesignThrough Graphics, 1st, ©
2000. Printed and Electronically reproduced by permission of
Pearson Education, Inc., Upper Saddle River, New Jersey.)

54. VISUALIZING AND DRAWING
COMPLEX CYLINDRICAL SHAPES
Steps

55. CYLINDERS WHEN SLICED
Cylinders are often machined to form plane or other types of surfaces.
Normal surfaces appear true shape in the view where the line of sight is
perpendicular to the surface. In the two other views that normal surface
appears on edge. The back half remains unchanged.

56. CYLINDERS AND ELLIPSES
If a cylinder is cut by an inclined plane, the inclined surface is bounded by
an ellipse. This ellipse will appear as a circle in the top view, as a straight
line in the front view, and as an ellipse in the side view.
When a circular shape is shown inclined in another view and projected into
the adjacent view it will appear as an ellipse, even though the shape is a
circle.

57. INTERSECTIONS AND TANGENCIES
Where a curved surface is tangent to a plane surface no line is drawn, but
when it intersects a plane surface, a definite edge is formed.
When plane surfaces join a contoured surface, a line is shown if they are
intersect, but not shown if they tangent.

58. Intersections of Cylinders
When the intersection is small, its
curved shape is not plotted
accurately because it adds little to
the sketch or drawing for the time it
takes. Instead it is shown as a
straight line.
When the intersection is larger,
it can be approximated by
drawing an arc with the radius
the same as that of the large
cylinder.

59. FILLETS AND ROUNDS
A rounded interior corner is called a fillet. A rounded exterior
corner is called a round.
(Courtesy of Ross Traeholt.)
(Courtesy of Douglas Wintin.)
Rounds on a CAD Model of a
Design for a Three-Hole Punch
Fillets on a CAD Model.

60. RUNOUTS
Small curves called runouts are used to represent
fillets that connect with plane surfaces tangent to
cylinders.
Runouts from different filleted
intersections will appear
different owing to the shapes of
the horizontal intersecting
members.

61. CONVENTIONAL EDGES
There is a conventional way of showing rounded and filleted edges for
the sake of clarity. Added lines depicting rounded and filleted edges.
Rounded and filleted intersections eliminate sharp edges and can make it difficult to
present the shape clearly.

62. NECESSARY VIEWS
One-View Drawing
Two-View Drawing
Three-View Drawing
What are the absolute minimum views
required to completely define an object?

63. PARTIAL VIEWS
A view may not need to be complete but needs to show what is necessary to clearly
describe the object. This is called a partial view and is used to save sketching
time and make the drawing less confusing to read.
You can use a break line to limit the partial view…
OR

64. Showing Enlarged Details
When adding a detail,
draw a circle
around the features
that will be included in
the detail
Place the detail view on the
sheet as you would a removed
view. Label successive details
with the word DETAIL followed
by a letter, as in DETAILA,
DETAIL B,

65. Conventional Breaks
To shorten the view of a long object, you can use break lines…
Using a break to leave out a portion of the part, but allows the scale for the ends
to be increased to show the details clearly.

66. ALIGNMENT OF VIEWS
Always draw views in the “standard” arrangement...
Because CAD makes it easy to move whole views, it is
tempting to place views where they fit on the screen or
plotted sheet and not in the standard arrangement. This
is not acceptable.
3D CAD software that generates 2D drawing views as
projections of the 3D object usually has a setting to
select from third-angle or first-angle projection. Check
your software if you are unsure which projection methods
are available.

67. REMOVED VIEWS
A removed view is a complete or partial view removed to another place on the sheet
so that it is no longer in direct projection with any other view.
Removed View Using
Viewing-Plane Line
Removed View Using
View Indicator Arrow

68. REVOLUTION CONVENTIONS
Regular multiview projections are sometimes awkward, confusing, or
actually misleading.
Revolutions like these are
frequently used in connection
with sectioning. Revolved
sectional views are called
aligned sections.

69. Common Hole Features Shown in
Orthographic Views

70. Common Features Shown in
Orthographic Views

71. Common Features Shown in
Orthographic Views Continued…

72. PAPER SIZE BORDER WIDTH (mm) DIMENSIONS OF
DRAWING SHEETS
(mm)
BOTH SIDES TOP & BOTTOM
A B
A0
A1
A2
A3
A4
20
20
10
10
10
20
20
10
10
10
1189 x 841
841 x 594
594 x 420
420 x 297
297 x 210
Sheets Frame
(Borderlines)

73. A1
A3
A5
A7
A6
A4
A2

74. Material or Parts List
The list should give the following information:
 The item or part number
 The part name
 The quantity required
 The material and its specification
 The drawing number of each individual part
 Other information considered appropriate

75. Revision Table
• A table of revision normally located in the upper right-hand
corner of the drawing frame
• It is important requirement in all drawing and design offices
• when minor revision are required, it is much easier to
revise an existing drawing than to create a new one
ZONE REF REVISION BY CKD DATE

76. Zoning
• Drawing may be divided into zones by a grid reference system based
on numbers and letters.
• Purpose: to assist location of detail. Particularly useful on large
drawing.
• Horizontal zones are designated by capital letter starting with A (top to
bottom)
• Vertical zones are designated by numbers reading from left to right.
1 2 3 4 5 6 7 8
A A
B B
C C
D D
1 2 3 4 5 6 7 8

77. ANY QUESTION ?

80. Exercise

83. Answer