@tig said:
I did get the cup analogy but I wasn't sure the others would !
Really, the cup analogy has pitfalls. First or Third, the right hand view will look identical, be it the hollow inside of the cup, or the bottom of the cup, both would result in a "donut" end view on either side. TRUNCATED CONE! Accept no substitutes.
@tig said:
... extract...
First-angle projection [FR/EU] is as if the object were sitting on the paper and, from the "face" (front) view, it is rolled to the right to show the left side or rolled up to show its bottom. It is standard throughout Europe (excluding the UK) and Asia.
First-angle projection used to be common in the UK, and may still be seen on historical design drawings, but has now fallen into disuse in favor of third-angle projection [US].
Third-angle projection [US] is as if the object were a box to be unfolded. If we unfold the box so that the front view is in the center of the two arms, then the top view is above it, the bottom view is below it, the left view is to the left, and the right view is to the right.
It is standard in the United Kingdom (BS 8888:2006 specifies it as the default projection system), USA (ASME Y14.3-2003 specifies it as the default projection system), and also in Canada, and Australia etc.
In 'first-angle projection' [FR/EU], the "top" view is pushed down to the floor, and the "front" view is pushed back to the rear wall; the intersection line between these two planes is therefore closest to the large end of the cone, hence the first-angle symbol shows the cone with its large end open toward the donut.
In 'third-angle projection' [US - and all sensible nations], the "top" view is pulled up to the ceiling, and the "front" view is pulled forward to the front wall; the intersection line between the two planes is thus closest to the small end of the cone, hence the third-angle symbol shows the cone with its large end away from the donut.
???
Just wanted to say, this is... yes, I know this post is 6 years old... still though, this is the best textual description of the difference between 1st & 3rd angle projection I've ever seen. Well done! Last I knew, UK was 1st angle... sounds like my info was out of date! Great to know, thank you! Reason I came to this post, was a Canadian drawing (I'm in US)... so this was helpful in adding weight to my suspicion.
It surprises me to see people w/ formal drafting training have no experience w/ these terms. That said, I admit they don't mean a lot for most people. However, the second you have international customers, these terms become amazingly important. Maybe this is less the case in architectural fields... probably less houses shipped overseas than "parts". Still, it is absolutely not an "over-complication", any more than it would be an "over-complication" to discriminate between inches and millimeters. If you assume a drawing is 3rd angle, and it's actually 1st angle, odds are, your part will be completely wrong. Vitally important. Possibly this will be less important when we stop all trade with the rest of the world. 
