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.

Graphics Word
language language

Line Projection Geometric

construction Lettering
types method
Drawing Standard

• A standard is a set of specifications for parts, materials or process

intended to achieve uniformity, efficiency and specific quality.
• Standards are set of rules that govern how technical drawings are
represented.
• Standard connect the world.
• Engineering Drawing is the Universal Language of Engineers, spoken,
read and written in its own way.
• BIS Drawing Codes: The representation of any matter by some sign or
mark on the drawing is known as convention or code, These
conventions are specified by bureau of Indian standards (BIS).
• BIS was formerly known as Indian standards Institute (ISI). The latest
BIS drawing codes are SP 46: 2003- Engineering Drawing Practice
For colleges.
Sheet Layout

• Sheet sizes: The preferred sizes of the drawing sheets recommended by the Bureau
of Indian Standards (B.I.S.) are given below as per SP: 46 (2003).

• Margin: Margin is provided in the drawing sheet by drawing margin lines. Prints
are trimmed along these lines. After trimming, the prints would be of the
recommended trimmed sizes of the trimmed sheets.
• Border lines: Clear working space is obtained by drawing border. More space is
kept on the left-hand side for the purpose of filing or binding if necessary.
• Borders and frames: SP: 46 (2003) recommends the borders of 20 mm width for
the sheet sizes AO and A 1, and 10 mm for the sizes A2, A3, A4 and AS.
• Folding marks: Folding marks are made in the drawing sheet. They are helpful in
folding of prints in proper and easy manner.
• Orientation mark: Four centring marks are drawn to facilitate positioning of the
drawing for the reproduction purpose. The orientation mark will coincide with one
of centring marks which can be used for the orientation of drawing sheet on the
drawing board.
• Grid reference system (zones system): The grid reference system is drawn on the
sheet to permit easy location on the drawing such as details, alterations or additions.
The rectangle of grid along the length should be referred by numerals 1, 2, 3 ... etc.
and along the width by the capital letters A, B, C, D etc.
• Revisions of drawing: For locating a portion of the drawing for the purpose of
revision etc., the sides of the three larger sizes of the drawing sheets viz. AO, A1 and
A2 are divided into a number of equal zones.

c
• Title block: It is in the bottom
right-hand corner of the d
Drawing space c
drawing sheet as shown in fig. Border
The size of the title block as lines
recommended by the B.I.S. is Title block
185 mm x 65 mm for all
designations of the drawing
c

sheets.
Line
• Lines are like the alphabet of a drawing language. Various types of lines are
used to construct meaningful drawings.
• A line may be straight, curved, continuous or segmented. It may be thin or
thick.

Appearance Name according

Types of Lines
to application
Continuous thick line Visible line

Continuous thin line Dimension line

Extension line
Leader line
Dash thick line Hidden line
Chain thin line Center line

Chain thin line and Cutting plane line

Thick at end only
Ruled line and short Long break line
Zig-zag thin
Line
Lettering

• Writing of titles, dimensions, notes and other important particulars on a

drawing is called lettering.
• Lettering should be done properly in clear, understandable & uniform style.
• 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.
➢ Thus, it must be written with

Legibility - shape
- space between letters and words

Uniformity - size
- line thickness
 Dimension & Notes

Notes Title Block

Basic Strokes

• Straight Slanted Horizontal Curved

Examples : Application of basic stroke

4 5
“I” letter 1 “A” letter 1 2 “B” letter 1

3 6

3
Upper-case letters & Numerals

Straight line
letters

Curved line
letters

Curved line
letters &
Numerals
Lower-case letters

• The text’s body height is about 2/3 the height of a capital letter.
Stroke Sequence

I L T F

E H
Stroke Sequence

V X W
•
N M K Z

Y A 4
•
O Q C G
• D U P B

R J 1 2
•

5 7
•
S 0 3 6

8 9
•

l i
•
v w x k

z
•
j y f t

r
• c o a b

d p q e
•
g n m h

u s
Word Composition

A) Non-uniform spacing B) Uniform spacing

JIRAPONG JIR A P O N G
Which one is easier to read ?

Spacing
JIRAPONG
\/ \
Contour |||| | )( )| |(
• General conclusions are:
• Space between the letters depends on the contour of the letters at an adjacent side.
• Good spacing creates approximately equal background area between letters.
• Leave the space between words equal to the space requires for writing a letter “O”.
Guidelines for lettering

• Standard height for uppercase or capital letters and numerals according to

the Bureau of Indian Standards (BIS) is 1.8, 2.5, 3.5, 5, 6, 10, 14, 20 mm.
The size for a particular drawing is selected according to the size of the
drawing.
• Drawing numbers, title block, and letters denoting the cutting planes and
sections are written in 10 mm size.
• Drawing title is written in 7 mm size.
• Hatching, subtitles, materials, dimensions, notes, etc., are written in 3.5 mm
size.
• Space between the lines is 3/10 h (height of capital letters).
• Space between the words may be equal to the width of the alphabet M or 3/5
h (height of capital letters).
Guidelines for lettering

• For technical drawings, single stroke vertical capital Gothic letters are used.
Dimensioning

• Dimensions are indicated on the drawing to define the size characteristics such as
length, breadth, height, diameter, radius, angle and location of hole, slot, etc.
• They should be mentioned directly on the drawing to describe a component clearly
and completely in its finished form.
➢ Dimension line: Dimension line is a thin continuous line. It is terminated by
arrowheads touching the outlines, extension lines or centre lines.
➢ Extension line: An extension line is also a thin continuous line drawn in extension
of an outline.
➢ Arrowhead: An arrowhead is placed at each end of a dimension line.Its pointed end
touches an outline, an extension line or a centre line. The length of the arrowhead
should be about three times its maximum width.
➢Leader: A leader or a pointer is a thin continuous line connecting a note or a
dimension figure with the feature to which it applies.
System of Dimensioning

• There are two systems of placing the dimensions : (1) Aligned system and (2)
Uni- directional system.
1. Aligned System: In the aligned system the dimension is placed perpendicular
to the dimension line in such a way that it may be read from the bottom edge or
the right-hand edge of the drawing sheet. The dimensions should be placed
near the middle and above, but clear of the dimension lines.
2. Unidirectional system: In unidirectional system all dimensions are so placed
that they can be read from the bottom edge of the drawing sheet. The
dimension lines are broken near the middle for inserting the dimensions.

Aligned System Unidirectional system

General rules for dimensioning

1. Dimensioning should be done so completely that further calculation or assumption of

any dimension, or direct measurement from the drawing is not necessary.
2. Every dimension must be given, but none should be given more than once.
3. A dimension should be placed on the view where its use is shown more clearly.
4. Dimensions should be placed outside the views, unless they are clearer and more
easily read inside.
5. Mutual crossing of dimension lines and dimensioning between hidden lines should
be avoided. Dimension lines should not cross any other line of the drawing.
6. An outline or a centre line should never be used as a dimension line. A centre line
may be extended to serve as an extension line.
7. Aligned system of dimensioning is recommended.