Understanding the First Angle Projection vs Third Angle Projection in Engineering Drawings

Understanding the First Angle Projection vs Third Angle Projection in Engineering Drawings

The primary means of graphic communication utilized in engineering is multi-view orthographic projection

Engineering Drawings consist of how and how objects are created. All techniques are built on the orthographic projection.

Multi-view is a technique that uses 2 or more projections of an object in an orthographic projection to convey the shape and dimensions of the object, so that the shop or job site has all the information necessary to create it.

To create a 2D view of a three-dimensional object, orthographic projection is used. These are created by drawing parallel lines to show the views of an object onto a flat surface.

What is an Orthographic Projection?

In orthographic projections, every different angle of an object is projected onto a plane, as if someone was looking at the object from the other side.

The included reference planes are:

  • Horizontal Plane (HP)
  • Vertical Plane (VP)
  • Side or Profile Plane (PP)

The included view point are:

  • Top View (TV) – Projected on HP
  • Front View (FV) – Projected on VP
  • Side View (SV) – Projected on PP

Orthographic projection technique can create two types of drawings:

  1. Multi-view drawings where each view depicts an item in two dimensions
  • All three dimensions are displayed in a single view in axonometric drawings

When a three-dimensional object is on a plane, it’s only shown adequately in a two-dimensional image. Either not enough of the object can be seen or certain parts are distorted. For the most accurate representation, another method has to be used.

Projection can be seen by observing shadows cast onto a two-dimensional surface, proving that the object is projected there.

The orthographic projection system is used to illustrate 3D objects with lines onto a surface.

First Angle Projection vs. Third Angle Projection

Orthographic views: The conventional three different orthographic viewpoints are visible in both first angle and third angle projection of a given part or assembly. The primary distinction between the first angle and third angle method is the design of the component on the sheet.

In Engineering Drawings What is a First Angle Projection?

Orthographic projection is the most popular way to acquire engineering drawings. It has three views: top, front, and edge. The vertical plane at right angles to the viewer is also a fundamental element in this technique, as it is in angle projection, which is accepted everywhere but the US and Japan. Views are created by positioning your object so it appears above the horizontal plane and aligns with the vertical plane.

Attributes of First Angle Projections in Engineering Drawings:

  • Positioning of the the object is in the first quadrant
  • They are mostly used in countries like India, Canada & Europe
  • The Projection plane is opaque
  • The front perspective is represented by top of the axis
  • The object is positioned directly between the two in First Angle Projection, and not in Third Angle Projection

What is the Third Angle Project in Engineering Drawings?

3D objects are realistically shown in 3D on a 2D screen with the perspective projection technique. The US primarily uses third angle projection for its industrial designs, which require transparency to create the most realistic effect. Thus in the third angle projection the projection planes are transparent

The following are the Characteristics of Third Angle Projection in Engineering Drawings 

  • These are typically US and Australia
  • The object is placed at one end projection plane in the middle and the observer at the end
  • Positioning of the object is in the third quadrant
  • The front perspective is represented by the bottom of the horizontal axis
  • The left side of the vertical axis has left view

The language of graphics or drawings has a greater importance to designer, technician, sanitarian and engineer which used to communicate designs to others. It is written in the form of shape, size and specifications of physical bodies.

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