orthographic projection in engineering drawing we often have to produce 2d and 3d drawings of parts are components these 3d objects need to be shown on 2d planes that is x and y planes in such a way that we get to see all the views that is front view side view top view etc this projection system is known as orthographic projection and in this system of projection the views have to be drawn following certain standard projection rules that is first angle and third angle method the first and third angle methods are largely used in any designing industry to understand this we first need to learn about the quadrant system in quadrant system we have got two planes in 2d that is x and y plane or horizontal and vertical planes respectively when the axes of the 2d system divide the plane into four infinite regions these regions are known as quadrants these quadrants are designated in an anticlockwise direction starting from the first quadrant that is upper right corner to the last which is lower right corner fourth quadrant rule of orthographic projection according to this rule to draw the projection of a 3d object on the 2d plane the horizontal plane is rotated in the clockwise direction first angle method in the first angle method the object is placed in the first quadrant such that it lies between the viewer in the plane of projection while considering the observer is standing here view from this point is considered as the front view when the viewer views the object from the front view its projection is projected on the vertical plane of the first quadrant you can see from the viewer's eye how the front view of this object looks and when the viewer views the object from the top its top view is projected on the horizontal plane of the first quadrant this is how the top view looks from the top for the left-hand side view we consider another parallel plane which is placed on the right side of the object and when the viewer views the object from the left-hand side of the object the left-hand side view is projected onto the profile plane this is how it looks for the right-hand side view we consider another parallel plane on the left side of the object and when the viewer views the object from the right-hand side of the object the right-hand side view is projected onto the profile plane which is placed on the left side of the object this is how it looks for drawing these projections onto the drawing sheets we follow the rule of orthographic projection according to this rule to draw the projection of a 3d object on the 2d plane the horizontal plane is rotated in the clockwise direction and the profile planes are also unfolded by doing so we have the following projections the front view of the object is on top the top view is on the bottom the left hand side view is on the right side of the front view and the right hand side view is on the left side of the front view this is how we draw on drawing sheets using the first angle method if you are enjoying this video please give this video a thumbs up as it helps the youtube algorithm to recognize good content and suggest others who want to learn and if you are new to adtw learn click on the subscribe button and turn on the notification to get more informative videos like this third angle projection method in this projection method the object is placed in the third quadrant and the plane of projection lies between the object and the viewer as the vertical plane of the third quadrant lies between the viewer and the object the viewer cannot see the object therefore we will make the vertical plane transparent and then we can see the front view which will be projected on the vertical plane lying between the viewer and the object similarly while viewing from the top the horizontal plane will come between the point of view in the object therefore the top view will be projected on the horizontal plane for the right-hand side and left-hand side view we will have the two profile planes on either side of the object now when the viewer sees from the right side the right side view will be projected on the right profile plane of the third quadrant and the left side view will be projected on the left profile plane when we unfold the planes according to the orthographic rule we will get a front view on the bottom of the xy line a top view on the above xy line and left side view on the left side of the front view and a right side view in the right side of the front view this is how first and third angle projection method works symbols used to represent these are the symbols used for representing first angle and third angle method why don't we use the second angle and fourth angle method it is not possible to show a 3d view of an object on the 2d plane therefore we use orthographic projection according to the rule of orthographic projection the horizontal plane needs to be rotated in the clockwise direction to view the top and front view on the 2d plane once the horizontal plane is rotated in the clockwise direction the projections present on the horizontal plane are also rotated along with the plane now consider the second angle view in which the object is placed on the second quadrant and the plane lies between the object and the viewer the top view is projected on the horizontal plane and the front view is projected on the vertical plane and when the horizontal plane is rotated in the clockwise direction the top view projected on the horizontal plane will overlap with the front view projected on the vertical plane a similar problem will occur while using the fourth quadrant therefore we don't use the second in the fourth angle method i hope you have understood the first and third angle methods it takes lots of effort to make such informative videos you can help adtw learn to make more videos by joining our channel and contributing to developing more such videos your support will help us make great educational videos other ways of helping us is by sharing our 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