Gentlemen and experts,

According to ASME B16.5 para. 6.4.5.3 (2013), average roughness for serrated flange facing is between 3.2 μm to 6.3 μm(125 μin. to 250 μin.) .
But according to my experience this range is so smooth and will not match with serration. I checked many standard flanges and none of them had roughness less than 50 μm so how is it possible to have the serration (usually with rough surface) at this range? please advice me on this matter.

Regards