Diameter
The diameter is the distance across the centre of a round (cylindrical) cross-section – e.g. in screws, drills, threads.
Distinctions:
- Outer diameter – the outermost edge of an external thread.
- Minor diameter (for internal thread) – inner part without thread flanks.
Practical example:
For a metric thread M6, the outer diameter is approximately 6 mm (measured at the flank tips), while the minor diameter is smaller – important for the core hole in thread cutting.