- Technical drawing
- Ananta
- March 2, 2021

In this detailed guide to various**Types of scales in technical drawing**, we will discuss**technical drawing standards**and its designation for use on all technical drawings in all fields of engineering.

table of Contents

## What is a scale in engineering drawing?

The standards in technical drawing are the**Ratio of the linear dimension of an element of an object as represented in the original drawing to the actual linear dimension of the same element of the object itself**.

The scales in the technical drawing are**a series of levels or numbers used in a particular system as a parameter of measurement or comparison.**Engineering scales are manufactured in a variety of grades to meet the needs of many different types of engineering jobs. The engineering scale chosen for the drawing should affect the level of precision required for scaled measurements on prepared drawings.

## Full scale, enlarged scale, and reduced scale in construction drawings

It is not always possible to draw an object in its actual size. For example, drawings of very large objects cannot be plotted to full size because they are too large to fit on the drawing sheet. Again, drawing a very small object cannot be drawn at full size because it would be too small to draw and read.

Different types of scales are used in engineering drawings to accommodate objects and draw and read them conveniently, as follows:

**Full scale:**When a technical drawing is made at the actual size of the object, the scale used is called the full-size scale, and the drawing is called the full-size drawing.

*A scale with a 1:1 ratio is called a full-size scale.**in technical drawing.*

Example: A smooth disk with a radius of 30 mm is represented in the drawing by a circle with a radius of 30 mm.

**Magnification Scale:**If a very small object, such as B. components of a wristwatch, is enlarged in some regular proportion to accommodate its drawing. So if the drawing is made larger than the actual size, the scale is called the enlarged scale, and the drawing is called the enlarged drawing.

*A scale where the ratio is greater than 1:1.*

**reducing scale:**If the object is large, the actual dimensions of the object must be reduced to accommodate the object drawn on the drawing sheet. So when a drawing is made smaller than the actual size of the object, the scale used is called the reduction scale and the drawing is called a reduced drawing.

*A scale where the ratio is less than 1:1*.

## Representative Portion (RF)

The representative fraction is defined as the ratio between the dimension of an element of an object in the drawing and its actual linear dimension of the same element of the object itself.

The value of R.F is always expressed in the form of** x:y,**in which both

*Y*

**X***are lengths converted to the same units. Therefore, RF has no decimals or units.*

**j**RF for full size scale = 1

RF to scale down <1

RF for magnification scale > 1.

He also emphasizes that RF is the ratio of linear dimensions and not the ratio of areas or volumes. If the quantities are in units of area, take the square root to convert them to units of length. When quantities are in units of volume, take the cube root to convert to units of length.

## Designation of scales in technical drawings.

The full designation of an engineering scale consists of the word "SCALE" followed by an indication of their relationship, as follows:

1:1 SCALE for full size;

SCALE X :1 for magnification scales;

SCALE 1: X for reduction scales

## BIS recommended scales on technical drawings

The BIS recommended RF default values for engineering drawing scales are as follows.

- Full scales - 1:1
- Reduction scales: 1:2, 1:5, 1:10, 1:50, 1:100, 1:200, 1:1000, 1:2000, 1:5000
- Scales of increase: 50:1, 20:1, 10:1, 5:1, 2:1.

The scales to choose in the construction drawing depend on several factors such as the size of the object and the functionality of the drawing.

## The prerequisite for the construction of a scale in the technical drawing.

The information required for the construction of flat, diagonal or vernier scales is the following:

- rf scale
- The maximum length to be measured by the scale.
- The minimum length the scale should measure (i.e., the smallest count)

He*scales length*in the technical drawing is determined by the formula:

*Länge der Skala*=*representative faction**X**be of maximum length* *Measured.*

## Types of scales in technical drawings:

Scales on engineering drawings are classified as follows:

- simple scale
- diagonal scale
- Ninth Scale
- reference point
- scale chords

### simple scale

On a simple scale, a line divided into an appropriate number of equal parts or units, the first of which is divided into smaller parts.

The use of the simple scale in the engineering drawing is to measure up to two consecutive units, that is, a unit and its immediate subdivision.

For example, meters and decimeters, feet and inches, etc.

### diagonal scale

A diagonal scale is used when measurements are required in three consecutive units, that is, h a unit and its two immediate subdivisions. Measuring a diagonal scale is more accurate than measuring a simple scale.

For example (a) meters, decimeters and centimeters.

### Ninth Scale

A vernier scale is used to measure three consecutive units on a metric scale. Therefore, the measurement precision of the vernier is equivalent to that of a diagonal scale. Vernier scales on engineering drawings are used to indicate distances in one unit and its two immediate divisions.

The vernier scale consists of two parts: (a) main scale and (b) vernier scale.

The vernier is an auxiliary scale attached to one end of the main scale. Since it is difficult to divide the minor divisions of the major scale in the usual way, this is done with the help of the vernier.

Most often, the vernier is used in length measuring devices such as calipers, micrometers, and micrometers.

#### Direkter Nonius o Vorwärts-Nonius

With direct vernier, the smallest division of the main scale is greater than the smallest division of the vernier scale.

The smallest subdivision of the major scale (*X*)>The smallest division of the vernier scale(*j*).

The lesser count of the direct vernier;*(x-y)*

#### Retrograde vernier scale or reverse vernier scale

With retrograde vernier, the smallest division of the main scale is smaller than the smallest division of the vernier scale.

The smallest subdivision of the major scale (*X*)<The smallest division of the vernier scale(*j*).

The lesser count of the direct vernier;*(y-x)*

#### I don't know twice

In the double vernier, two single verniers are placed next to each other to form a single scale with a zero in the middle. One vernier is used for clockwise reading and the other vernier for counterclockwise reading.

When the divisions on the main scale are marked in both directions (ie, clockwise and counterclockwise) from common zero, a double vernier is required.

Example: aAbney level.

### reference point

A comparison scale is a pair of scales that share a common representative fraction, but are graduated to read measurements in different unit systems.

For example: A map has been drawn with an engineering scale showing that kilometers and hectometers can be measured directly into miles and furlongs using a comparative scale made with the same representative fraction or RF.

### chord scale

If a protractor is not available, a string scale can be used to measure the angle or set the required angle. Constructions are based on chord lengths measured on the bow itself.

## Additional information about scales in technical drawings

The scale to choose for a drawing depends on the complexity of the object and the purpose of the representation.

In either case, the scale should be large enough to allow for easy and unambiguous interpretation of the information presented.

Details that are too small for full dimensioning in the main representation should be shown in a separate large-scale detail view (or section) next to the main representation.

It's a good idea to add a full-screen view to the large-scale representation of a small object for information. In this case, the full-size view can be simplified by showing only the outlines of the object.

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