I with this technical drawing.

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Discussion Overview

The discussion revolves around interpreting a technical drawing, specifically identifying whether it uses first or third angle projection, understanding specific elements indicated by arrows, and the relevance of projection types in practical settings.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • Participants inquire about distinguishing between first and third angle projection based on the provided drawing.
  • One participant suggests that the red arrow points to a dimension line or extension line, indicating its relevance to the drawing's features.
  • Another participant describes how to visualize the top view in relation to the lower view, emphasizing practical understanding over theoretical projection types.
  • There is uncertainty regarding the identification of the black dot indicated by the orange arrow, with one participant speculating it may relate to a specific dimension mentioned in the drawing.
  • Concerns are raised about the necessity of knowing the projection type, with a participant noting that professionals may not prioritize this knowledge in practice.

Areas of Agreement / Disagreement

Participants express differing views on the importance of identifying the projection type, with some focusing on practical aspects of the drawing while others seek clarity on technical details. The discussion remains unresolved regarding the specific identification of the projection type and the elements indicated by the arrows.

Contextual Notes

There is a lack of consensus on the significance of first versus third angle projection in professional practice, and assumptions about the drawing's context may not be fully articulated.

Wangtang1
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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?
 
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i think you did not upload the picture correctly.
 
Sorry, here is the picture.

http://img222.imageshack.us/img222/9988/engineeringdrawing.jpg
 
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Wangtang1 said:
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
 
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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.
 

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