## First Angle and Third Angle Projection Methods | Engineering Drawing

To provide details of 2D drawing of any 3D object, two main types of projections are used and they are

A collection of 2D drawings of any 3D object is represented with the help of orthographic projection. Orthographic projection consist of 6 views (Front, Back, Top, Bottom, Right, Left) called as principle views. Among these six orthographic views front view, right view and top view are the most commonly used to represent the orthographic projection of any object.__First Angle projection__and__Third Angle projection__.#### Method of Projection

Now, we know there are basically four quadrants. Hence to get the projections, we divide the object into four quadrants. First quadrant represents the

**First Angle projection**of the object while third quadrant represents the**Third Angle projection**of the object. The principle projection planes and quadrants used to create 2D drawings can be seen in fig. 1.Fig. 1. Principle Projection Planes and Quadrants |

Now, let us see first angle and third angle projection in details.

####
__First Angle Projection__

In first angle projection, the object is placed in between the plane of projection and the observer as shown in fig.2.

Fig.2. Object in between Plane of projection and observer |

__Right Hand Side view__on the left side of the front view. Similarly, bottom plane is unfolded towards the bottom to obtain the

__Top view__placed below front view as shown in fig. 3.

Fig.3. First Angle Method |

#### Third Angle Projection

In third angle projection, the plane of projection is placed in between the object and the observer as shown in fig.4.

Fig.4. Plane of projection in between object and observer |

In this type of projection, the object is placed in third quadrant. The views are obtained by projecting the image on the respective plane as shown in fig.5.

Fig.5. Third Angle Projection |

#### Symbols

As per BIS standard, drawing symbol for first angle projection and third angle projection are shown in fig.6.

Fig.6. Projection Symbol |

#### Difference in between First Angle projection and Third Angle Projection

Due to increase in complication in drawings, second angle projection and fourth angle projection are not used. The difference between first angle projection and third angle projection is given below.

First Angle and Third Angle Projection Methods | Engineering Drawing
Reviewed by Unknown
on
16:12
Rating:

## No comments:

Post a Comment