The document discusses different types of scales used in technical drawings. It describes engineering scales, graphical scales, and representative fractions. The main types of scales covered are plain scales, diagonal scales, comparative scales, and vernier scales. Requirements for constructing scales are also provided, including representative fraction, maximum measurable length, and least count. Scales allow drawings to be made at different sizes relative to the actual object, such as full size, reduced size, or enlarged size.

1. scales
Team members : Bhavana SINGH, D.INDRA SENA REDDY, G.SAI TEJA ,GIRIDHAR JEE,HARSH
KUMAR

2. contents

3. introduction

4. introduction
The word ‘ scale’ usually employs for an instrument used for drawing or measuring the
length of a straight line. It is also used to represent the proportion in which a drawing is
made with respect to the size of the object . When a drawing is prepared to the actual
size of the object, the scale is said to be full size scale and the drawing is said to be
full size drawing. When a drawing is prepared smaller than the actual size of the
object, the scale is said to be reduction scale and the drawing is said to be reduce
sized drawing. When the drawing is prepared larger than the actual size, the scale is
said to be an enlargement scale and the drawing is said to be enlarge sized drawing
i.e. drawing of an electronic instrument .

5. Representation
Of
scales

6. Representation of scales
A scale can be expressed in one of the following ways:
1. Engineering scale: Engineering scale is represented by indicating the
relation between the dimension on the drawing and the corresponding actual
dimension of the object. They are usually written on the drawings in
numerical forms.
2. Graphical scale: Graphical scale is expressed by its representative fraction
and is captioned on the drawing itself.

7. Representative
fraction

8. Representative fraction
Representative fraction(R.F) is defined as the ratio of the
linear dimensions of an element of the object in the
drawing to its actual linear dimension of the same element
of the object itself.
R.F = length of an element in drawing
actual length of the same element

9. Types
Of
scales

10. Types of scales
Scales are classified as the following:
1. Plain scale
2. Diagonal scale
3. Comparative scale (plain and diagonal type)
4. vernier scale
5. Scale of chords

11. PLAIN SCALE : A plain scale is used to measure up to two
consecutive units, i.e., a unit and its immediate sub
division. For example, (a) meter and decimeter, (b)
kilometer and hectometer, (c) feet and inches, etc.
DIAGONAL SCALE : A diagonal scale is used to represent
three consecutive units, i.e., a unit and its immediate two
sub divisions. For example, (a) meter, decimeter and
centimeter (b) kilometer, hectometer and decameter, (c)
yards, feet and inches, etc. A diagonal scale can measure
more accurately than a plain scale.

12. COMPARATIVE SCALE : Comparative scale is a pair of scales having a common representative
fraction but graduated to read different units. A map drawn in miles and furlongs can be
measured directly in kilometers and hectometers with the help of a comparative scale.
Comparative scales may be either plain or diagonal scales depending upon the requirement
VERNIER SCALE : A vernier scale is used to measure three consecutive units of a metric scale.
Thus, the measuring accuracy of the vernier scale is equivalent to that of a diagonal scale. The
vernier scale consists of two parts: (a) a main scale and (b) a vernier. The vernier is an auxiliary
scale that is attached at one end of the main scale. As it is difficult to subdivide the minor
divisions of the main scale in an ordinary way, it is done with the Scales 4.25 help of the vernier.
Most often, the vernier scale is used on length measuring devices such as vernier calipers and
micrometers. Vernier scales are of two types namely direct ver nier and retrograde vernier. Both
are equally sensitive and easy to read.

13. Requirements
Of
a
scale

14. Requirements Of a scale
The data required for the construction of a plain, a diagonal or a vernier scale are as follows:
1. RF of the scale.
2. The maximum length which the scale can measure.
3. Least count of the scale, i.e., minimum length which the scale can measure.
The following steps are required in construction of all types of scales except the scale of
chords.
1. Determine the value of R.F.
2. Calculate the length of scale as Ls = R.F * Maximum length. It is usually expressed in cm.
3. Actual drawing of the scale.

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