All Junior Cert Technical Graphics posts
• #### Isometric Scale: Arcs? StudyStudent

Hi,

Does anybody know how to draw the arcs in the isometric question using the isometric scale method?

For example, the elevation of the object shows a part of a circle with a radius of 25mm. From my understanding, you draw this portion of the circle out again and divide it up. Although I'm not entirely sure what to do next.

1. #### StudyStudent

I'll explain in detail what I usually do.

I usually...

1. ... look for the radius of the circle given

2. ...find the radius, lets take 25mm as an example

3. ...draw the axes of the isometric projection

4. ...draw out a quarter of the circle again

5. ...mark in 10mm from the centre of the circle, and another 10mm from the new point

6. ...I stop, and puzzle over what to do next for the next ten minutes!

Does anybody know a.) whether I'm doing this correctly up until number six and b.) what I do next?

2. #### thomasreilly

Instead of 5 I would do:

5. Draw 60 degrees and 30 degrees from the centre of the circle

6. Draw a line vertically down with from the points where the 30 and 60 degree lines hit the circumference

7. Where the points hit the bottom of the circle label them h1 and h2

8. scale them down on your 45 - 60 thingy

9... tell me when you get this far..

45 - 30*

4. #### StudyStudent

@thomasreily

Thanks for the help. I'm a bit late getting back to you, so I understand if you don't get the time to continue your reply before the exam.

I think I understand this better now. I attempted a few questions, with the help of your instructions, and I think my drawings turned out as they should.

Thanks again, and good luck.

5. #### Me

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