# 1st Angle And 3rd Angle Projection Pdf

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Third Angle projection is a method of orthographic projection which is a technique in portraying a 3D design using a series of 2D views. 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.

## 3rd Angle Projection

Orthographic Projection is a way of drawing an 3D object from different directions. Usually a front, side and plan view are drawn so that a person looking at the drawing can see all the important sides. Orthographic drawings are useful especially when a design has been developed to a stage whereby it is almost ready to manufacture. They differ only in the position of the plan, front and side views.

Below is an example of F irst Angle projection. Opposite is a simple L-shape, drawn in three dimensions. The front, side and plan views have drawn around the 3D shape. However this is not the correct way of drawing them as they are not in the right positions. The correct method of presenting the three views, in first angle orthographic projection is shown below. The drawing is composed of a front, side and plan view of the L-shaped object.

The first drawing is the front view drawn looking straight at the front of the L-shape , the second is a drawing of the L-shape seen from the side known as side view and last of all a drawing from above known as a plan view.

The red lines are faint guidelines and they are drawn to help keep each view in line, level and the same size. Please Note! This is an example of first angle orthographic projection as used mainly in Europe.

There is another type called third angle which is used by countries such as the USA. Some people call this a birds eye view. Draw an orthographic projection of a H-shape. Clearly show the front, side and plan views and use guidelines to keep them level. Carefully study the symbols shown below.

Normally when drawing in first or third angle projection a symbol is drawn underneath which clearly shows which angle of projection has been used. Follow the blue, red and green guidelines as the front, side and plan view are constructed.

The final arrangement of the views are shown in the drawing below. Notice how the symbol for first angle orthographic projection has been added and the paper has a title block and borderline. Select a simple three dimensional object and draw it in first angle projection. The front, side and plan views are in different positions. Now imagine standing directly in front of the L-shape, the drawing opposite shows exactly what you would see. The plan view is a view seen directly from above.

Another example of first angle orthographic projection is shown below.

## Teaching the Theory of 1st and 3rd Angle Orthographic Projection

First angle projection and Third angle projection are two different methods of creating a 2D drawing of a 3D part. First Angle Projection is commonly used in all countries other than United States. It is mainly used in Europe and Asia countries. Following table describes what is the difference between or comparison between First Angle Projection vs Third Angle projection. Following are the details description of first angle projection vs third angle projection given in text note from above table for better readability. Also Read Mechanical Engineering Basics.

## What is first angle orthographic projection?

The orthographic projection system is used to represent a 3D object in a 2D plane. The orthographic projection system utilizes parallel lines, to project 3D object views onto a 2D plane. According to the rule of orthographic projection. To draw a projection view of a 3D object on a 2D Plane. The horizontal plane is rotated in the clockwise direction.

Orthographic Projection is a way of drawing an 3D object from different directions. Usually a front, side and plan view are drawn so that a person looking at the drawing can see all the important sides. Orthographic drawings are useful especially when a design has been developed to a stage whereby it is almost ready to manufacture. They differ only in the position of the plan, front and side views.

Third Angle projection is a method of orthographic projection which is a technique in portraying a 3D design using a series of 2D views. 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. The images below show the projection of the object on a 3D box surrounding the object. The box is then gradually unfolded to then present a series of 2D views in the 3rd Angle projection as viewed by the observer.

We will keep adding more information on why 2nd and 4th angle projection systems are not used to create engineering drawings. Orthogonal Projection. Third- and First-Angle Projections.

### What is The Difference Between First And Third Angle Projection? A Mechanical Engineer Explains

This is one of the most common topics of discussion in the community of mechanical engineers and designers alike. Ask any professional with a hands-on experience of design and tools, he or she will say this is nothing but the means of representing three-dimensional objects in two dimensions. First and third angle projection are nothing but ways of describing what an object looks like from different directions. This is called orthographic projection and orthographic is nothing but engineering drawings or plan views. This is one of the most common methods used to obtain engineering drawings, mostly for orthographic projections. Orthographic projection is a graphical method used to represent three-dimensional structures or objects into different perspective projection images called views. The orthographic view typically consists of the top view, front view, and the side view.

Most likely you have knowledge that, people have look numerous times for their favorite books next this first and third angle projection, but end taking place in harmful downloads. Symbol for third angle projection shown on dwg. Third Angle VS First Angle Description: Both third angle and first angle projection display the standard three orthographic views of a part or assembly. Therefore the word orthographic stands for drawing at right angle. Third angle which is used in USA.

Every engineer must know how to read engineering drawings and the most integral part of this is knowing the difference between first and third angle projection. A collection of 2D drawings can be used to represent a 3D object in orthographic projection and consists of six orthographic views Top, Bottom, Right, Left, Front and Back view also known as six principle views. Out of these six, front, right side and top view are the most commonly used ones. But how do you get these orthographic views from a 3D object?

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