I with this technical drawing.

[Wangtang1]

http://img268.imageshack.us/img268/9...ingdrawing.jpg

How can I tell whether this is third or first angle projection? What is the big line at the top that the red arrow is pointing at? Is an external thread used where the orange arrow is pointing at?

 

[Rajini]

i think you did not upload the picture correctly.

 

[Wangtang1]

Sorry, here is the picture.

http://img222.imageshack.us/img222/9988/engineeringdrawing.jpg

 

[Rajini]

http://img268.imageshack.us/img268/9...ingdrawing.jpg

How can I tell whether this is third or first angle projection? What is the big line at the top that the red arrow is pointing at? Is an external thread used where the orange arrow is pointing at?

Hi,
I totally forgot about 1st and 3rd angle projections Sorry i cannot tell you which projection.
Red arrow: It should be the dimension line or extension line (it is the extension line)
If you draw a straight vertical line below the red arrow it reaches a 'hole' and this 'hole' corresponds to the six holes in the bottom figure. These six holes are written in your bottom figure as 85 PCD 6 Dia 1-6 pitch.
Orange arrow: Your ornage arrow points towards a black dot. I really don't know what it is. Bur it could be associated to 20 Dia 2 pitch as seen in bottom figure.
Hope it helps

 

[pongo38]

If you take the top view and imagine holding it in your hands, one hand each side; then rotate the top of the view towards you so that you are looking in the direction of the red arrow, then that is what the lower view looks like. Who cares which angle projection it is? I went round a professional drawing office and not one draughtsman could tell me which projection they were using ("that's just something we did at college, but nobody bothers with it"). You haven't illustrated section A-A, but whatever it is, it could be positioned anywhere convenient on the same drawing or another drawing.