introduction to Eng drawing

1. Overview of an Engineering Drawing
Mettu University
Technology Faculty
Mechanical Engineering Department
By Mr Leliso H.

2. ♦ Define graphic communication
♦ Mention some types of drawing
♦ Explain the difference between different types of
drawings
♦ Mention some of the applications of technical
drawings
Objectives

3. •What is drawing ?
•What is graphics language ?
•List some types of drawing ?
•What is standard of drawing ?
•List types of line we use in drawing ?
•What is lettering ?
CHAPTER ONE
INTRODUCTION TO GRAPHIC
COMMUNICATION

4. Drawing (Graphics language)
A drawing is a graphic representation of an object,
or a part of it and is the result of creative thought by
an engineer or technician.
Any medium that uses a graphic image to aid in
conveying a message, instructions, or an idea is
involved in graphic communication.

5. Technically, it can be defined as “a graphic
representation of an idea, a concept or an entity which
actually or potentially exists in life. Graphic
communication involves using visual materials to
relate ideas.
Cont…

6. Drawing as a means of communications
• Exchange of ideas needs means of
communication. As the idea becomes technical
the usual means of communication (talk or
listen, read or write) will be less exact. For this
reason visual language is developed to be
technical and accurate means communication.
This visual language in broad term is called
graphic language.

7. • The v-block is to be made of cast iron and machined on
all surfaces. The overall sizes are two and one-half
inches high, three inches wide, and six inches long. A
v-shaped cut having an included angle of 90° is to be
made through the entire length of the block. The cut is
to be made with the block resting on the three inch by
six inch surface. The v-cut is to begin one-quarter inch
from the outside edges. At the bottom of the v-cut there
is to be a relief slot one-eighth inch wide by one-eighth
inch deep.
Cont…

8. Cont…

9. Effectiveness of Graphics Language
The word languages are inadequate for describing the
size, shape and features completely as well as
concisely.
1. Try to write a description of
this object.
2. Test your written description
by having someone attempt
to make a sketch from your
description.
You can easily understand that …

10. Graphic language in “engineering application” use
lines to represent the surfaces, edges and contours
of objects.
A drawing can be done using freehand, instruments
or computer methods.
Composition of Graphic Language
The language is known as “drawing” or “drafting” .

11. Graphic Language or Drafting
– It is a form of communication that is technical
and very exact.
– It is visual language
– Utilize line and symbols agreed all over the world.
Graphic communication  written or drawn

12. • The most common names associated with
the graphic languages are:
– Drafting : represent all graphic languages.
– Technical Drawing : Any drawing which
expresses technical ideas, including sketches,
instrument drawings, charts, and illustrations.
Eg. Technical Sketching; Freehand.
Cont…

13. Types of Drawing
There are two basic types of drawings:
•Artistic drawings and
•Technical drawings.
Artistic Drawings
Artistic Drawings range in scope from the simplest line
drawing to the most famous paintings. Regardless of their
complexity, artistic drawings are used to express the feelings,
beliefs, philosophies, and ideas of the artist.
In order to understand an artistic drawing, it is sometimes
necessary to first understand the artist.

14. Cont…

15. Cont…
Technical Drawings
The technical drawing, on the other hand, is not subtle, or
abstract. It does not require an understanding of its creator,
only an understanding of technical drawings.
A technical drawing is a means of clearly and concisely
communicating all of the information necessary to
transform
an idea or a concept in to reality. Therefore, a technical
drawing often contains more than just a graphic
representation of its subject. It also contains dimensions,
notes and specifications.

16. Cont…

17. Types of Technical
Drawings
• Three Basic Types of
Technical Drawings
– Freehand sketches
– Instrument drawings
– Computer drawings
and models

18. Freehand drawing
The lines are sketched without using instruments other
than pencils and erasers.
Example

19. Instrument drawing
Instruments are used to draw straight lines, circles, and
curves concisely and accurately. Thus, the drawings are
usually made to scale.
Example

20. Computer drawing
The drawings are usually made by commercial software
such as AutoCAD, solid works etc.
Example

21. Engineering
Drawing

22. Elements of Engineering Drawing
Engineering drawing are made up of graphics language
and word language.
Graphics
language
Describe a shape
(mainly).
Word
language
Describe size, location and
specification of the object.

23. Basic Knowledge for Drafting
Graphics
language
Word
language
Line
types
Geometric
construction Lettering
Projection
method

24. Drawing Standard

25. Drawing Standard
Standards are set of rules that govern how technical
drawings are represented.
Drawing standards are used so that drawings convey
the same meaning to everyone who reads them.

26. Drawing Sheet
Trimmed paper of
a size A0 ~ A4.
Standard sheet size
(JIS)
A4 210 x 297
A3 297 x 420
A2 420 x 594
A1 594 x 841
A0 841 x 1189
A4
A3
A2
A1
A0(Dimensions in millimeters)

27. Drawing Scales
Scale is the ratio of the linear dimension of an element
of an object shown in the drawing to the real linear
dimension of the same element of the object.
Size in drawing Actual size
Length, size
:

28. Drawing Scales
Designation of a scale consists of the word “SCALE”
followed by the indication of its ratio, as follow
SCALE 1:1 for full size
SCALE X:1 for enlargement scales (X > 1)
SCALE 1:X for reduction scales (X > 1)
Dimension numbers shown in the drawing are correspond
to “true size” of the object and they are independent of
the scale used in creating that drawing.

29.  Definition:
- Line is the most basic design 'tool'.
- A line has length, width, tone, and texture.
- It may divide space, define a form, describe contour,
suggest direction.
Examples:
"A line is a dot that went for a walk." - Paul Klee.

30.  1. Visible Lines: Dark, heavy lines with approximate width 0.6mm.
 Show the outline and shape of an object.
 Define features you can see in a particular view.
 2. Hidden Lines: Light/medium, narrow, short dashed lines with
approximate width 0.3mm.
 Shows the outline of a feature that can not be seen in a particular
view.
 Used to help clarify a feature, but can be omitted if they clutter a
drawing.

31.  3. Section Lines: Thin lines usually drawn at a 45 degree angle.
Indicate the material that has been cut through in a sectional
view.
 4. Center Lines: Thin line consisting of long and short dashes.
Shows the center of holes, slots, paths of rotation, and
symmetrical objects.

32. 5. Dimension Lines: Thin, dark lines.
 Show the length, width, and height of the features of an object.
 Terminated with arrowheads at the end.
6. Extension Lines: Thin line used to show the starting and
stopping points of a dimension.
 Must have at least a 1mm space between the object and the
extension line.
Dimension
Line
Extension
Line

33. 7. Leader Lines: Thin lines.
 Used to show the dimension of a feature or a note that is too large
to be placed beside the feature itself.
8. Cutting Plane Lines: Thick broken line that is terminated with
short 90 degree arrowheads.
 Shows where a part is mentally cut in half to better see the interior
detail.
Leader Line

34. 9. Break Lines: Used to break out sections for clarity or for
shortening a part.
 Three types of break lines with different line weights.
 a. Short Breaks. Thick wavy line.
 Used to break the edge or surface of a part for clarity of a hidden
surface.
 b. Long Breaks. Long, thin lines.
 Used to show that the middle section of an object has been
removed so it can be drawn on a smaller piece of paper.
 c. Cylindrical Breaks. Thin lines.
 Used to show round parts that are broken in half to better clarify
the print or to reduce the length of the object.

35. 10. Phantom Lines: Thin lines made up of long dashes alternating
with pairs of short dashes.
 Three purposes in drawings.
1.To show the alternate position of
 moving parts.
2. To show the relationship of parts
 that fit together.
3.To show repeated detail.
 Phantom lines can show where a part is
moving to and from.
 Eliminates the confusion of thinking there may be 2 parts instead of
just 1.
Phantom Lines

36. Drawing Tools

37.  In engineering drawing any object is represented by
straight lines and/or curves. These lines should be
drawn as accurate as possible by the help of drawing
instruments.
 Quality of a drawing depends to a large extent on
the quality , adjustment, proper use and care of
drawing instruments.
DRAWING TOOLS

38. DRAWING BOARD
Drawing tables come in many
different size and design. It could
be fixed, movable, with drawer,
adjustable, etc.
They are used to attach drawing
sheet.
Keep your drawing table clean
and dry not to affect your
drawing quality.
Don’t use blades to cut
drafting tapes on drawing
table.

39. 1. T-Square
– They can be made from different
materials, mostly from wood or
plastic.
– Parts: blade and head
– two edges of the blade should be
parallel.
– The head is fixed at 900 to the
blade
– The cleanness of your T –square
greatly affect your drawing
quality and cleanliness.

40. 2. Triangles
Triangles
Used to draw lines at
standard angles and by
connecting any two points

41. 3. Adhesive Tape 4. Pencils
2H or HB for thick line
4H for thin line

42. 5. Sandpaper
6. Compass used to draw circles
or
arcs (which are parts of a circle)

43. 7. Pencil Eraser 8. Erasing Shield
DRAWING TOOLS

44. 9. Circle Template 10. Tissue paper
DRAWING TOOLS

45. 11. Sharpener 12. Clean paper
DRAWING TOOLS

46. A few basic points for a drawing
• Should be complete and unambiguous
• Should be neat and easy to read
• Use only as many views as necessary to
show all required detail
• Apply tolerances realistically - overly
tight tolerances can add a great deal of
additional cost with little or not added
value to the part

47. ABCDEFGHIJKLMNOPQRS
TUVWXYZABCDEFGHIJKL
MNOPQRSTUVWXYZABCD
ABCDEFGHIJKLMNOPQRS
TUVWXYZABCDEFGHIJKL
MNOPQRSTUVWXYZABCD
EF
Lettering

48. Text on Drawings
Text on engineering drawing is used :
To communicate nongraphic information.
As a substitute for graphic information, in those instance
where text can communicate the needed information
more clearly and quickly.
Uniformity - size
- line thickness
Legibility - shape
- space between letters and words
Thus, it must be written with

49. Lettering Standard
In this course
Use only a vertical Time New Roman text style,
Use all capital letters.
Use 4 mm for most text height.
Space between lines of text is at least 1/3
of text height.

50. Basic Strokes
Straight Slanted CurvedHorizontal
1 1 2
3
Examples : Application of basic stroke
“I” letter “A” letter 1
2
3
4 5
6
“B” letter

51. Suggested Strokes Sequence
Straight line
letters
Curved line
letters
Curved line
letters &
Numerals
Upper-case letters & Numerals

52. GOOD
Not uniform in style.
Not uniform in height.
Not uniformly vertical or inclined.
Not uniform in thickness of stroke.
Area between letters not uniform.
Area between words not uniform.
Example : Good and Poor Lettering

53. Leave the space between words equal to the space
requires for writing a letter “O”.
Example
Sentence Composition
ALL DIMENSIONS ARE IN
MILLIMETERS
O O O
OUNLESS
OTHERWISE SPECIFIED.O

54. THANK YOU