- Engineer Design
- March 2, 2021
In this detailed guide to variousTypes of scales in technical drawing, Let's discusstechnical drawing standardsand its designation for use on all technical drawings in all fields of engineering.
What is a scale in the technical drawing?
The scales in the construction drawing are theRelationship between the linear dimension of an element of an object as represented in the original drawing and the actual linear dimension of the same element of the object itself.
The scales on the design drawing area series of levels or numbers used in a particular system as a measurement or comparison parameter.Engineering scales are manufactured in a variety of grades to meet the needs of many different types of engineering work. The technical scale chosen for the drawing affects the required accuracy of the scale measurements on the drawings produced.
Full scale, enlarged scale and reduced scale in engineering drawings
It is not always possible to draw a full-size object. For example, drawings of very large objects cannot be plotted at full size because they are too large to fit on the drawing sheet. Again, drawing a very small object cannot be a full-size drawing because it would be too small to draw and read.
There are several types of scales used in engineering drawings to allow objects to be accommodated and plotted and read conveniently, as follows:
full deflection:When a technical drawing is made for the actual size of the object, the scale used is called the actual size scale, and the drawing is called the actual size drawing.
A scale with a 1:1 ratio is called a full-size scale.in technical drawing.
Example: A flat disk with a radius of 30 mm is represented in the drawing by a circle with a radius of 30 mm.
enlarged scale:If a very small object, such as B. components of a wristwatch, is enlarged by a regular ratio in order to adapt it to its design. Therefore, if the drawing is made larger than the actual size, the scale is called enlarged scale and the drawing is considered enlarged drawing.
A scale where the ratio is greater than 1:1.
Reduce scale:If the object is large, the actual dimensions of the object must be reduced to accommodate the object drawn on the drawing sheet. Thus, 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 known as the reduced-size drawing.
A scale where the ratio is less than 1:1.
Representative portion (RF)
The representative proportion 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 R.F value is always expressed in the form ofx:y,in which bothXejare lengths converted to the same units. Therefore, RF has no decimal and has no units.
RF to full size scale = 1
RF to scale down <1
RF to magnification range > 1.
It should also be noted that RH is the ratio of linear dimensions and not the ratio of areas or volumes. In this case, the quantities are given in units of area, so take the square root to convert them to units of length. When quantities are in units of volume, use the cube root to convert to units of length.
Designation of scales in technical drawings
The full designation of a technical scale consists of the word "SCALE" followed by the statement of its ratio, as follows:
SCALE 1:1 for original size;
SCALE X :1 for magnification scales;
SCALE 1: X for reduction scales
Scales recommended by BIS in engineering drawings
The BIS recommended standard RF values for rulers in engineering drawings are as follows.
- Full scale - 1:1
- Reduction Scales - 1:2, 1:5, 1:10, 1:50, 1:100, 1:200, 1:1000, 1:2000, 1:5000
- Extended scales - 50:1, 20:1, 10:1, 5:1, 2:1.
The scales in the construction drawing should be chosen because they depend on several factors such as the size of the object and the functionality of the drawing.
The requirement for the construction of scales in the technical drawing.
The information needed to create flat, diagonal, or vernier scales is as follows:
- Skala Rf
- The maximum length to be measured by the scale.
- The minimum length to be measured by the scale (i.e. smallest count)
Öscale lengthin the technical drawing is determined by the formula:
scale length=representative factionXbe maximum length measured.
Types of scales in technical drawings:
Scales in engineering drawings are classified as follows:
- simple scale
- Diagonal Scale
In plain scale, a line divided into a reasonable number of equal parts or units, the first of which is divided into smaller parts.
The use of the simple scale in engineering drawing is to measure up to two consecutive units, i.e. one unit and its immediate subdivision.
For example – meters and decimeters, feet and inches, etc.
A diagonal scale is used when measurements are required in three consecutive units, ie one unit and its two immediate divisions. Measuring a diagonal scale is more accurate than measuring a plain scale.
For example (a) meters, decimeters and centimeters.
A vernier scale is used to measure three consecutive units of a metric scale. Therefore, the measurement accuracy of the vernier corresponds to that of a diagonal. Vernier scales on engineering drawings are used to indicate distances in a 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 subdivide 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 linear measuring devices such as calipers, micrometers and micrometers.
Direkter Nonius oder Direkter Nonius
With the direct vernier, the smallest division of the main scale is larger 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 lowest direct vernier number;(x-y)
Retrograder Nonius oder retrograder Nonius
With the 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 lowest direct vernier number;(y-x)
double vernier scale
In the double vernier, two simple verniers are placed end to end to form a single scale with zero in the middle. One vernier is used to read clockwise and the other vernier is used to read counterclockwise.
When divisions on the major scale are marked in both directions (i.e. clockwise and counterclockwise) from the common zero, a double vernier is required.
A comparative scale is a scale that has a common representative fraction, but is graduated to read measurements in different systems of units.
For example: a map drawn with an engineering ruler showing kilometers and hectometers can be directly measured in miles and furlongs using a comparison ruler constructed with the same representative fraction or RF.
If a protractor is not available, a chord scale can be used to measure the angle or define the required angle. Constructions based on chord lengths of angles measured on the same arc.
Additional information about scales in engineering drawings
The scale to choose for a drawing depends on the complexity of the object and the purpose of the representation.
In any case, the scale chosen must be large enough to allow easy and unambiguous interpretation of the information presented.
Details that are too small to be shown to scale in the main illustration must be shown in a separate, large-scale detailed (or sectional) view next to the main illustration.
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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