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Discussion in 'Mistakes, Blunders and Boo Boos' started by deverett, Jun 10, 2011.
Bob nice clear by the book explanation.
oops. so i did. thanks for pointing it out Bob.
another reason to stick to the back-o-the-envolope sketches LOL
So what happened to the second angle?
The Emerald Isle
I just finished a 6-month vo-tech class on blueprint reading. The textbook uses 3rd angle for all the drawings, but has a page explaining 1st angle. It states that "3rd angle has been used exclusively in the US and Canada since the early 20th century... However the 1st angle method continues to be used in most all of the other industrial nations."
You really want to complicate things don't you
In the UK, industry moved over to 3rd angle years ago, but the model engineering world still seems to favour 1st.
and Kvom writes:
It states that "3rd angle has been used exclusively in the US and Canada since the early 20th century... However the 1st angle method continues to be used in most all of the other industrial nations."
So, which is it?
perhaps the model engineering world is mostly in all of the other industrial nations ;D
Whether you use 1st angle or third angle projection is stated on the blueprint or drawing by using the correct sign.
Most modelengineers often do not notice that sign.
Most of western Europe are using third angle projection drawing. That is generally taught at schools and colleges.
This symbol tells it all
Straight from a US publication
Theoretically the object might be placed in any of the four angles or quadrants, projected to the planes and the planes folded about their intersection. Practically the second and fourth angles would be eliminated, leaving only the first and third as possibilities.
I guess the answer is nothing happened it just seemed like a smart idea to give it a miss.
From what I have read : 1st angle is the ISO and Asian standard projection and 3rd angle is the standard US,Canada, UK and Australian projection. Certainly up to the 1960's 1st angle was the usual projection used in Oz and the UK, although 3rd angle was permitted. I guess we were in transition.
I like this image. it breaks it down very easily.
the 'FR' shows 1st angle pretty well : the right image is what happens, if you flip the left hand object over to the right.
The 'US' shows 3rd angle : the right image is what happens if you LOOK AT the left image FROM the right.
I think it's easy to see why 3rd angle makes so much more sense.
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