This document discusses the alphabet of lines, which are different types of lines used in technical drawings to convey specific meanings. It explains that drawings use lines similar to how written language uses letters, with lines like object lines, hidden lines, and section lines serving as the "alphabet." The document also provides examples of common line types and their appearances, and background on drawing scales and sheet sizes.

1. Application of the alphabet of lines
In this unit we are going to look at lines, which are an
important part of drawing.
Drawing is a graphic language used by engineers and
draughts persons.
It is made up of symbols, dimension, notes and
different types of lines which transmit meaning.
Unit2

2. • Written language has letters of the alphabet to form
words and sentences. The language of drawing uses
a number of different types of lines, called the
alphabet of lines, to transmit the meaning of a
drawing.
When you execute an engineering drawing, you
should always keep the following in mind:
i. Correctness
ii. Accuracy
iii. Speed
iv. Correct layout of the drawings on a drawing sheet.

3. Study objectives
After studying this unit, you should be able to draw and identify the
following lines:
(1) Object lines
(2) Centre lines
(3) Dimension lines
(4) Extension lines
(5) Leader lines
(6) Hidden lines
(7) Dashed lines
(8) Break or Cutting Line
(9) section lines

4. Basic Line Types
Name according
to application
Types of Lines Appearance
Continuous thick line Visible line/ Object lines
Continuous thin line Dimension line
Extension line
Leader line
Dash thick line Hidden line
Chain thin line Center line

7. Letters

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

13. Scales
Introduction
All Drawings are usually either too large or too small and to
be their true size.

14. Drawing Scales
Designation of a scale consists of the word “SCALE”
followed by the indication of its ratio, as follow
SCALE 1:1
SCALE X:1
SCALE 1:X
for full size
for enlargement scales
for reduction scales

15. Drawing space Drawing
space
Title block
d
d
c
c
c
Border
lines
1. Type X (A0~A4) 2. Type Y (A4 only)
Orientation of drawing sheet
Title block