Bollocks, spent 10 minutes posting a reply only for it to disappear.

this has got to be the crappies web site known to man.

OK ignore the 3D views.

Take to top example and using the side view, that's the one on the right, 'roll' the cone to the left and you will get two circles, both visible. One roll so that's First angle projection.

Now take the second example and to get the side view to resemble the end view you have to 'roll' it 3 times, hence third angle projection.

Typical yankee operation trying to make out because 3 is bigger than 1 it's better.

That's why they don't have ground floors and their ground floor is the first floor so building are higher. same as staing vehicle weights as 80,000 pounds is far bigger than 35.7 tonnes.

Hi I am just as baffled as Woolfie! three pictures duplicated one above the other but the top two are the opposite way round to the bottom two .If you put them all upside down they are still the same six pictures.I know that Iam past my sell buy date but I also have never been taught the difference and I still cannot see it .help please.

Maurice B.

Oh well, let me try my definition.

We have two drawings of the same thingie, one to the left, the other to the right.

First angle: the picture on the right side shows the item as seen looking from left.

Third angle: the picture on the right side shows the item as seen looking from right.

In the case of that truncated cone it does not make much difference, but this also serves only to show which type of drawing it is. As was already told, in drawings of more complex nature it can make all the difference.

By the way, all drawings I get in my semi-professional work are in first angle.

Greetings, Hansrudolf

It hasn't been made clear that the PURPOSE of the symbols is to show how the different views are arranged.

It isn't hard to imagine a drawing with a front view, plan and two side views, where it isn't possible to be sure which of the two side views goes on the right and the left of the object.

If you know the projection used, then it is easy to work out which is which.

With third angle each side view is next to the end of the elevation it represents and the plan is above the top of the object. You can imagine folding them back around a box to make a 3-d model of thE object.

With first angle the views are adjacent to the side opposite the one they represnt. As has been mentioned you can imagine turning the object through 90-degrees to one side, and drawing the view that faces upwards.

The little sketches are just an unambiguious way of showing which projection has been used.

Neil

Wikipedia has a good page on it.

Glad it's not just me struggling 

Chris

Edited By chris j on 16/09/2012 14:56:23

What do you make of this? on a drawing received (from the UK) a while ago.

Michael, Are we back to school days (70 years ago for me) when it was Plan, Side View and End View ? Bill

Most (probably all) drawing standards require hidden lines (or further views) to be used if the design intent is unclear without. In this case, with no hidden lines, the legitimate assumption is that it's a solid, truncated cone (frustrum).

That's possible with many 2D CAD systems which in many ways are really just manual extensions of the old drawing boards onto the screen. In that case if the user isn't "fluent" in projection systems misteaks can happen. (Although young or not, anyone producing drawings professionally should at least be able to get the projection right …. and where's the checker anyway? {rhetorical]).

Modern 3D CAD systems operate differently however and once the configuration is set to the projection system of interest (1st or 3rd), drawing view production and placement is handled by the program and will be correct.

With respect, Dave, the kind of gyrations you describe, (while fairly typical of toolrooms and machine shops) are more of a sign of people who are not completely comfortable with drawing projection systems than anything else. Experienced Engineers and Draftsmen do none of that. They simply look at the drawing and "see it".

An analogy is parallel parking a car between two oher vehicles at the kerbside. Novice drivers have have all sorts of rules …. line up this corner of the car with whatever …. now turn the wheel until something else lines up …. now turn the wheel back etc. The experienced driver just drives the car into the space, backwards.

Edited By Sid Herbage on 17/09/2012 02:03:16

Wierd,

I read this thread when Wolfie posted and didn't know what he was getting at – not struck the problem I suppose.

Just recieved a new copy of ME, and there on the bottom of some plans were these symbols.

now I have to go back and see if i understand them. – this board keeps finding more interesting things I don't understand (yet)

Dave

Also look on P37

And to further confuse the issue only 1st angle is a projection.

In 1st angle you draw the projected side view in the direction you see it.

In 3rd angle the side view is rotated 3 times and not projected.

Wolfie,

The graphic on p38 shows:

First Angle … Object inside the corner of a box with [let's say] cardboard walls

Third Angle … Object inside the corner of a box with [let's say] tracing paper walls

In photographic terms it would be the difference between using "Front-Projection" and "Back-Projection" screens.

Does that help?

MichaelG.