3rd Angle Projection & 1st Angle Projection

[digitalcarbon]

I'm learning ISO standards and I now understand metric and, as they say,  "never want to go back"

 

However, while I understand 1st Angle Projection I do not understand why it is used.

 

When a person sketches something, they hold the paper up in front of them and then look at an object in the distance for the Front View. (person, paper, object)

 

Then if you want the Right Side View you walk to the right of the object and place the image on the right of the Front View that you just drew..(person, paper, object)

 

BUT

 

for 1st Angle Projection 

 

You draw like you hold the paper behind the object (person, object, paper)

 

So you end up with the Right Side View to the left of the Front View.

 

So are you telling me that there are people on this planet who, when they draw a house, walk to the Right Side of the house but draw it on the LEFT side of the Front View???

 

What is the rational for 1st Angle Projection?

 

Why would anyone want to use it?

 

Sometimes you draw a dashed line from the right side of the Front View to the Right side view to show that something is the same height. But if the Right Side View is on the left of the Front View then you cannot do this...

 

What am i not understanding?

 

 

 

 

 

 

 

 

[Christiaan]

It's really just a matter of convention which method you use (or what you reader is expecting). Similarly to whether you draw window schedules viewed from the outside or inside of the window. In NZ I learnt to use third angle.

 

Main thing is to ensure you have a key for the reader to indicate which method you've used.

Edited October 19, 2017 by Christiaan

[digitalcarbon]

but why 

[Christiaan]

There is no why. People will prefer one or the other just because they're used to it. A bit like the choice between showing a schematic window schedule from the inside or the outside.

 

If you want a real world drawing metaphor that I learnt in tech drawing class as a young fella, then think of third angle projection as tracing paper, placing the paper over the drawing. And think of first angle projection as carbon paper, placing the paper under the drawing.

[Art V]

It is a preference to use first or third angle, I prefer 3rd angle over 1st angle.

Not to mention that with first angle projection the top view is below the front view and the bottom view above the front view.

 

As they say over here with first angle projection the object is between the viewer and the projection surface.

With third angle projection the projection surface is the between the viewer and the object.

These descriptions are mostly meaningless for non-drafting non-technical people.

 

Though over here it is called first and third quadrant projection.

 

Personally I find third angle/quadrant projection easier to understand for most people than first angle/quadrant projection because the right hand side is also on the right hand side in the drawing and the top view is above the front view etc. and it is what I use by default.

 

Drawings should not be puzzles to solve for the recipient, so I keep it simple and just use third angle projection unless first angle projection is required by the client.

Edited October 20, 2017 by Art V