What Is Orthographic Projection?
Important Point
Orthographic views consist of one, two, or more separate aspects of an object taken from different directions & different sizes, generally at right angles to each other and arranged in a definite manner.
These views collectively describe the object. Orthographic views of any purpose can be represented by any one of the two systems of projection
The first angle projection and the third angle projection. It is named according to the quadrant in this which the object is imagined no place for purposes of line projection.
As far as any shape and size of the views are concerned, there is no difference between these two systems. The only difference lies in the relative positions of the various views. Indian Standards Institution recommends
(IS: 696-1972) both these systems leaving the choice to the discretion of the organization concerned. However, there are specific merits and demerits associated with each system. Students are advised to study both methods to meet the varying demands of different industries in the country.
To meet this end. Some chapters in this book are exclusively dealt with in the first angle projection, and some in the third-angle projection.
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Types of Orthographic Projection
Orthographic projection two different parts and also a different type of symbol as per below detail mention.
- First angle projection & First angle projection symbol
- Third angle projection & Third angle projection symbol
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First Angle Projection & First Angle Projection Symbol
In this, the object is imagined to be in the first quadrant. Because the observer normally looks from the right side of the quadrant to obtain the front view.
The objects will come in between the observer and the plane of projection.
Therefore, in this case, the object is to be transparent, and the projectors are imagined ta be extended from various points of the object to meet the projection plane. First, these meeting points when joined in the order form an image
This is the principle of the first angle projection. Thus in the first angle projection, any view is so placed that it represents the side of the object away from it.
First angle projection is merely used throughout all parts of Europe so that called European projection.
Most important of First angle projection symbol
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Third Angle Projection & Third Angle Projection Symbol
In this, the object is imagined to be placed in the third quadrant.
Again, as the observer is normally supposed to look from the right side of the quadrant to obtain the front view, in this method, the projection plane comes in between the observer and the object.
Therefore, the plane of projection has to be assumed to be transparent. The intersection of this plan with the projectors from all the points of the object would form an image on the transparent plane.
The third angle is the system in used North America and alternatively described as American projection.
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Making Orthographic Views
Front View
To draw the front view of an object in the first angle projection, the object which is assumed to be transparent is imagined to be in front of the vertical plane (first quadrant) as shown in.
The shape of the object, when viewing from the front.
Is obtained by joining in order all the meeting points of the projectors extended from the visible edges of the object. This is called a front view.
A similar treatment is repeated for the front view in the third angle projection, but with a transparent vertical plane imagined to be held in front of the object.
Here the shape of the object when viewed from the front is obtained by joining in order all the intersection points on the transparent plane of the projectors to the visible edges of the object
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Side View
The shape of some objects cannot be interpreted completely from the from and top views only.
In such cases, more information may be needed, and for this purpose, a third plane is imagined.
This is called an auxiliary vertical plane and is placed perpendicular to the first two planes.
A view can be obtained on to this plane in a way similar to that explained above. In the first angle method, if the auxiliary vertical plane is the place to the right of the object, a view is obtained on it by looking at the object from its left side.
It is then called a left side view. On the other hand, if the auxiliary vertical plane is placed to the left of the
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Top View
The projection on to a plane placed horizontally below the transparent object will reveal the shape of the object as viewed from below.
This view is called a top view, and the principle that is being followed is that of the first angle projection. Figure deals with a similar treatment in the third angle projection with a transparent plane placed horizontally below the object.
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Presentation of view
For presenting the views on a drawing sheet, irrespective of the method of projection, the horizontal plane, and the auxiliary vertical plane arc rotated till they come in the plane with the original vertical plane.
Now the three views of the object will be in the same plane, viz., the plane of the paper. These three views normally provide enough information to describe the shape and size of the object.
Above drawing shows the relative positions of the views in the first angle projection and below drawing n the third angle projection.
The method used for the projection is indicated by a distinctive symbol (presentation of view drawing No 1 .C and Presentation of view drawing No 2 C)
Third Angle Projection
3rd Angle project is where the 3D object is seen to be in the 3rd quadrant. It is positioned below and behind the viewing planes, the planes are transparent, and each view is pulled onto the plane closest to it. The front plane of projection is seen to be between the observer and the object.
First Angle Projection Symbol in Engineering
When the large end of the cone in the section view is closest to the top view, this is known as first angle projection. Traditionally, the first angle projection symbol is drawn with the top view on the left and the side view on the right.
Third Angle Projection Symbol Definition
Third angle projection drawing. The projection symbol used to represent third angle projection shows what you would see when looking at the cone from the left, drawn sitting to the left of the drawing of the front face of the cone.
Difference Between First Angle and Third Angle Projection
First angle projection and third angle projection are two methods used in technical drawing and engineering to represent three-dimensional objects in two dimensions. The main difference between these methods lies in the placement of the object and the projection planes.
1. First Angle Projection:
In first angle projection, the object is placed in the first quadrant (top-right) of the imaginary box surrounding it. The observer is assumed to be looking through the box onto the object. The projection planes are located between the observer and the object. These planes are labeled as the Frontal Plane (FP), Horizontal Plane (HP), and Profile Plane (PP).
2. Third Angle Projection:
In third angle projection, the object is placed in the third quadrant (bottom-left) of the imaginary box. The observer is assumed to be looking at the object from outside the box, as if the box is transparent. The projection planes are located on the opposite side of the object, away from the observer.
First Angle Projection Symbol Standards
This symbol indicates the projection method used in the drawing. When the large end of the cone in the section view is closest to the top view, this is known as first angle projection. Traditionally, the first angle projection symbol is drawn with the top view on the left and the side view on the right.
First Angle Projection Symbol Explained
This symbol indicates the projection method used in the drawing. When the large end of the cone in the section view is closest to the top view, this is known as first angle projection. Traditionally, the first angle projection symbol is drawn with the top view on the left and the side view on the right.
First Angle and Third Angle Symbol
The symbols commonly used to represent angles are:
- The degree symbol (°): This symbol is used to denote angles measured in degrees. For example, 45° represents a 45-degree angle.
- The prime symbol (′): This symbol is used to denote minutes, which is a unit of measurement for angles. For example, 30′ represents 30 minutes, which is 1/60th of a degree.
- The double prime symbol (″): This symbol is used to denote seconds, another unit of measurement for angles. For example, 20″ represents 20 seconds, which is 1/60th of a minute or 1/3600th of a degree.
3rd Angle Projection Symbol
In technical drawings, this symbol is typically placed in the lower-right corner of the drawing to indicate that the object is being projected into the four quadrants of the orthographic views. The orthographic views are typically displayed on the right side of the drawing, with the front view on the bottom, the top view above it, and the right-side view to the left.
What Is the Position of Object in Third Angle Projection?
In the third angle projection, the object is placed in the third quadrant. The object is placed behind the vertical planes and bottom of the horizontal plane. Third angle projection is widely used in the United States.
What Is the Symbol of First Angle Projection?
Large end of the cone nearest to the top view indicates the symbol for first angle projection. Small end of the cone nearest to the top view indicates the symbol for third angle projection.
What Is the Symbol for Third Angle Projection?
The symbol used to represent third angle projection in technical drawings and engineering design is a right-angle triangle with a number “3” placed inside it. The triangle is drawn with one side perpendicular to the base and the number “3” is positioned within the triangle. This symbol indicates that the object is being viewed from a position opposite to the one normally used in first angle projection.
Orthographic Projection Examples
For example, an orthographic projection of a house typically consists of a top view, or plan, and a front view and one side view (front and side elevations).
Drafting Orthographic Projection
orthographic projection, common method of representing three-dimensional objects, usually by three two-dimensional drawings in each of which the object is viewed along parallel lines that are perpendicular to the plane of the drawing.
What Is Orthographic Projection in Engineering Drawing?
An orthographic projection is a way of representing a 3D object by using several 2D views of the object. Orthographic drawings are also known as multiviews. The most commonly used views are top, front, and right side.
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