3/20/2023
Outline
Engineering Drawing
Importance of engineering drawing
(MEng 2061) Drawing instruments
Drawing scale
Chapter One
Alphabets of lines
Introduction
Lettering
2023 Academic Year
What is Drawing? Drawing as a Means of Communications
Drawing is a graphic language used to Exchange of ideas needs means of
express ideas. communication.
In other words it is one means of As the idea becomes technical the usual
communication. means of communication (speak or
It is used for: listen, read or write) will be less exact.
◼ Research and Development For this reason, visual language is
◼ Design developed to be technical and accurate
◼ Production means communication.
◼ Construction, and etc.
1
3/20/2023
Cont.. Elements of a Drawing
✓ A clear and precise engineering drawing requires
This visual language in broad term is both graphics and word languages.
called graphic language.
We call it universal language of Graphics language
industry when it is used for production Describe a shape (mainly).
purpose.
Word language
Describe an exact size,
location and specification
of the object.
Graphic Language or Drafting Cont..
◼ Technical Sketching: A technical
The most common names associated drawing used to proportion shape of ideas
with the graphic languages are: so that other can understand the shape of
things.
◼ Drafting: represent all graphic languages.
◼ Engineering Drawing: Drawing used by
◼ Technical Drawing: Any drawing which
engineers and other member of the
expresses technical ideas, including
design-engineering team to describe the
sketches, instrument drawings, charts, and
production of parts, shape, size and
illustrations.
material.
◼ Mechanical Drawing: A technical
◼ Computer Graphics: Use of computer as
drawing made with drafting instruments.
drafting instrument with printer or plotter.
2
3/20/2023
Ways to Create an Engineering Drawing Freehand sketch
Three Basic Types of Technical The lines are drawn using only pencil
Drawings and erasers on a blank or grid paper.
◼ Freehand sketches
◼ Instrument drawings
◼ Computer drawings and models
Orthographic sketch
Drawing : Using instruments Drawing : Using a computer
Drawing instruments are Computer aided drafting (CAD) software is used.
used to draw straight lines,
circles, and curves concisely Example
and accurately
Drawings are usually made
to scale
2D drawing Solid modeling
3
3/20/2023
Cont. 2. Drawing Instrument
In engineering drawing any object is
AUTOCAD, represented by straight lines and/or
software used for curves.
modeling for civil
eng’g 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 instruments includes; 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.
4
3/20/2023
Drawing Sheet Standard size of drawing sheet
made from different materials with ❑ Trimmed paper of a
different quality. Such as, paper, tracing size A0 ~ A4.
paper, tracing cloth, glass cloth or film. ❑ Standard sheet size
in (mm) (JIS)
Drawing sheets will determine selection
of pencil grade A4 210 x 297
A3 297 x 420
A2 420 x 594
A1 594 x 841
A0 841 x 1189
Drawing Sheet : Orientation & Margin T-square
5
3/20/2023
Set square Drawing pencils
Used for: Most drawing pencil leads are made
from graphite. They are usually made in
◼ Drawing horizontal
lines 17 degrees of hardness.
◼ Guiding triangles • 6B(softest and blackest) • H (medium hard)
• 5B(extremely soft) •
◼ Position drawing •
2H (hard)
4B extra soft) • 3H (hard, plus)
paper • 3B (very soft) • 4H (very hard)
• 2B (soft, plus) • 5H (extra hard)
• B (soft) • 6H (extra hard, plus)
• HB (medium soft) • 7H (extremely hard)
• F (intermediate, between • 8H (extremely hard, plus)
soft and hard) • 9H (Hardest)
Cont. Other Drawing instrument
◼ Selection of drawing pencil depends on; Dividers:- used to transfer distance
type and quality of drawing paper
how thick and dark you want the line to Compass:- used to draw circles or arcs
be. (which are parts of a circle)
◼ Pencils used on paper in engineering French Curves
drawing
◼ Used to draw irregular curves.
Grade of pencil Used to draw
◼ It is available to align at least three points
H Object lines, lettering
the curve to be drawn.
HB Dimensioning and boundary
line
6
3/20/2023
3. Drawing Scales : Definition Designation
Scale is a ratio between the linear dimension of a Designation of a scale consists of the word “SCALE”
drawn representation of an object and the actual object. followed by the indication of its ratio, as follows
SCALE 1:1 for full size
SCALE X:1 (X > 1) for an enlargement scales
SCALE 1:X (X > 1) for a reduction scales
Drawing scale is commonly found in a title block.
4. Alphabet of Lines 11 Main Line Types
The different lines and line symbols used on Visible Phantom
drawings form, a kind of graphic alphabet Hidden Viewing Plane
commonly known as the alphabet of lines. Center Break
Each line has a definite form and line weight. Dimension
The standard thick line weight varies from Extension
.030 to .038 of an inch.
Leader
The standard thin line weight varies from
.015 to .022 of an inch. Section
Cutting Plane
7
3/20/2023
Visible object Lines Hidden Lines
are thick dark solid (unbroken) lines Hidden Lines are thin dashed lines used
that are used on drawings to indicate to indicate a surface, edge, or contour
the edges and details of an object. of an object that cannot be seen, or is
Surface
hidden from view.
Edge
Center Lines Section Lines
Center lines are thin lines made up of Are thin “cross hatching” lines usually
alternating long and short dashes. drawn at a 45 degree angle.
They are used to indicate the center of Indicates the material that has been cut
symmetrical features, such as circles or through in a sectional view.
arcs.
They are used as an aid in dimensioning. Section
Line
8
3/20/2023
Dimension Lines Extension Lines
Dark, heavy lines. Used to show the starting and stopping
Show the length, width, and height of points of a dimension.
the features of an object. Must have at least a 1/16th space
Terminated with arrowheads at the between the object and the extension
end. line.
Extension Line
Dimension Line
Leader Lines Cutting Plane Lines
Thin lines. Are very thick lines that indicate where
Used to show the dimension of a an imaginary cutting plane passes
feature or a note that is too large to be through an object, for viewing or
placed beside the feature itself. sectioning purposes or to better see the
interior detail.
9
3/20/2023
Break Lines Short Break Lines
Are used to shorten a view, or to Thick wavy freehand sketched line.
eliminate repetitive details when an Used to break the edge or surface of a
entire view is not necessary. part for clarity of a hidden surface.
Three types of break lines with different
line weights. Short Break Line
◼ Short Breaks.
◼ Long Breaks.
◼ Cylindrical Breaks.
Long Break Lines Cylindrical Break Lines
Long, thin straight zig-zags lines. Thin lines.
Used to show that the middle section of Used to show round parts that are
an object has been removed so it can broken in half to better clarify the print
be drawn on a smaller piece of paper. or to reduce the length of the object.
10
3/20/2023
Short break & long break lines 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.
Alternate Position Relationship of Mating Parts
Phantom lines can show where a part is Phantom lines can also show how two
moving to and from. or more parts go together without
Eliminates the confusion of thinking having to draw and dimension both
there may be 2 parts instead of just 1. parts.
Phantom Lines
11
3/20/2023
Repeated Detail Summary
Phantom lines can show repeated detail Now that we have discussed the 11
of an object. main line types, you should be able to
do the following:
Saves the drafter time and the company
money. 1. Identify the alphabet of lines
2. Identify where the line types are
Less chance of drafter error. used.
3. Produce the lines with various
line weights.
Quiz-one (Identify & name the types of
lines on the illustration below) 5min. Answer for the quiz
1. Extension 2. Visible 3. Dimension 4. long break line
5. hidden 6. cutting plane line 7. hidden 8. section
9. center 10. phantom 11. leader line
12. Short break line 13. visible 14. extension
15. section
12
3/20/2023
5. Lettering Good & poor lettering
Lettering plays a major role in Text’s style on the
drawing must have the
➢ overall appearance of a drawing and following two (2)
➢ increases the readability of the drawing. properties
Lettering should be executed in one
stroke as much as possibly.
Lettering Style (this course) Basic Strokes
Gothic lettering= Lettering having all the alphabets or
numerals of uniform thickness
Begin the sentence, phrase or word
with a capital letter.
Text height 2~3 mm.
Space between lines of text is about of
text height.
Height of the lower-case letter is about
2/3 of that of a capital letter.
13
3/20/2023
Suggested Stroke Sequences for Suggested Strokes Sequence for
Upper-case Letters & Numerals Lower-case Letters
❑ The text’ s body height is about 2/3 the height of a
Straight line capital letter.
letters
Curved line
letters
&
Numerals
Stroke Sequence : Upper-case Cont..
14
3/20/2023
Cont.. Cont..
Cont.. Cont..
15
3/20/2023
Cont.. Stroke Sequence : Lower-case
Cont.. Cont..
16
3/20/2023
Cont.. Cont..
Word Composition Observe the following word
Space between the letters depends on
the adjacent contour of the letters.
Non-uniform
spacing General conclusions are:
Space between the letters depends on the contour of
Uniform
the letters at an adjacent side.
spacing
Good spacing creates approximately equal background
❑ Word having non-uniform spacing is more readable area between letters.
17
3/20/2023
Space between Letters Cont..
1. Straight - Straight 3. Straight - Slant 5. Curve - Slant 6. Slant - Slant
2. Straight - Curve 7. The letter “L” and “T”
4. Curve - Curve
Sentence Composition
Leave the space between words equal
to the space requires for writing a letter
“O”.
18
