In technical drawings, orthographic two dimensional views are drawn at right angles to represent three dimensional objects. These views are drawn mainly using two schemes. One is the first angle projection and the other one is the third angle projection. The third angle projection is mostly used in America, Japan, and Australia while the rest of the world uses the first angle projection scheme.
In this article, we will mainly see what is the symbol for third angle projection of and how to remember it easily. Before that, please read the article “First Angle Projection Symbol – What is it – How to remember“. I will list down some important points to remember as well.
Note: There is no engineering logic behind this explanation. Many people often forget the symbol for the projections and this is just my way of imagination to remember it.
I hope you clearly understood how to remember the first angle projection symbol using the previous article. Below is the image for reference. Let’s continue from where we left.
We imagined the car as the circle (side view of the conical frustum) and the binocular as the front view of the conical frustum.
Since the car moves forward towards the observer in the image, it passes him and goes behind. See the image below. Now, this is the scenario to remember the third angle projection symbol.
The car is on the left side of the image and the observer is on the right side of the first image. Pay attention to the observer’s binocular, it still points to the initial direction of the car. Now, let’s take this scene and create the symbol from it.
Replace the car with the circle and replace the binocular with the front view of the conical frustum in the same direction as the binocular. i.e. the larger end on the right side and the smaller end on the left side. Add center lines and you get the third angle projection symbol.
Look at the first image where the first angle projection is explained. When we say binocular, the first thing we imagine is looking at the objects in front, correct? So, I remember this “first imagination” as the first angle projection symbol and the other scenario is the third angle projection.
It is the symbol used to represent the third angle projection in drawings. The parts are imaginably placed in the 3rd quadrant to produce the views.
USA, Canada, Japan, and Australia use third angle projection. Many companies that work for the above counties regardless of their locations use third angle projection.
You can find hundreds of drawings in this website all use third angle projection. From sheet metal, pipes, Gears to casting and plastic parts, you can download many drawings for free.
I have explained how to remember third angle projection symbol in a very very simpler method. Using this, you will never forget the correct symbol again.
Here is some more information about projections.
- In third angle projection, the object is placed in 3rd quadrant.
- It is important to specify projection type in a drawing, This is mandatorily included in every title block.
- Every CAD software has the ability to change the projection type in each and every drawing or in all drawings by default.
- Thin lines or grayscale lines are used in projection views incase the view contains a rounded surface.
That’s all for this topic. I hope this has helped you. Browse this site or use the search box to read more useful articles.