> For the complete documentation index, see [llms.txt](https://jamesbrayy.gitbook.io/atar/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://jamesbrayy.gitbook.io/atar/engineering/core/engineering-drawings.md).

# engineering drawings

***

## types of lines (in order of precedence):

* visible lines
  * continuous and thick (0.5 - 0.6 mm) line is used to represent all visible edges and boundaries.
* hidden lines
  * a dashed and medium thick (0.35 - 0.45 mm) line is used to indicate hidden edges and boundaries that cannot be seen.
* centre lines
  * a repeating long dash followed by a short dash and thin (0.3 mm) line is used to represent axes of symmetry for any circular, cylindrical, or spherical shapes.
* all dimensions are in millimetres (not metres)
* scales are always written as drawing : actual
* it is essential to know how to convert both from isometric to orthographic and from orthographic to isometric:
  \*

  ```
  ![](/files/rr6GdIKv4W7SB8vPUu8L)
  ```

  \*

  ```
  ![](/files/Qk0kl6dt94kETXsr73VM)
  ```