# Flange nut design

What is the difference between bearing circle diameter and flange diameter in context of prevailing torque flange nut? I see that maximum value for flange diameter and minimum value for bearing circle diameter are defined while designing. Does this mean actual flange diameter on the nut can be any value between (including) these two values?

• The Bearing Circle Diameter is the diameter that bears on the surface underneath ($$d_w$$ on the drawing below). It is the diameter you would want to know when calculating contact area, friction, pressure, etc.
• The Flange diameter is the outer diameter of the flange ($$d_c$$ on the image below) - it the the diameter that you would want to know if you were making sure the nut would fit in a counterbored hole

This image is from ISO 4161:2012(E)

• Is it possible that values of dw and dc may be same in some cases? Sep 6 '19 at 13:52
• Not for an ISO 4161:2012 flange nut, no. The radius f is a 'full round', so it couldn't have a sharp corner without an infinitely thin flange. Sep 6 '19 at 22:42
• I am not sure if other standards (eg inch sizes) allow this - what is the application, what nuts are you choosing between, and why does this matter? Sep 6 '19 at 22:43
• Hey @tims89 - did this answer your question? If so - please mark it as accepted so that the site knows not to keep bumping this onto the homepage, as that then buries the unanswered questions. If not, please update your question with more information regarding what you need to know? Sep 9 '19 at 8:45