Question

The complete circle of $\phi d$ and the incomplete circle of $\phi 0.8d$ in the top view of a vertical grub screw with diameter ‘d’ are drawn to __________
 

• A. represent conventionally the external V-thread.
• B. attain the neatness of the figure.
• C. represent conventionally the internal V-thread.
• D. attain the 3D effect of the circles.

Hint:

Use full and partial circles to represent internal threads in top view; major diameter = $d$, minor = $0.8d$.

Answer 1

The Correct Option is C

In engineering drawings, thread representation uses standard conventions.
When drawing a top view of a threaded object such as a grub screw (which typically contains internal threads), two circles are used:
- One full circle with diameter $\phi d$ (major diameter)
- One partial (dashed or broken) circle with diameter $\phi 0.8d$ (minor diameter)
This symbolic representation indicates internal V-threads that follow standard metric thread design.
The use of $\phi 0.8d$ represents the root of the internal thread, while $\phi d$ is the crest.
This system helps engineers interpret internal threads at a glance without unnecessary complexity.
Hence, the correct answer is Option (C).