I geddit now.
Great!
I had previously measured the angle of my NSC on an optical comparator at work equipped and found the angle to be approximately 14.5° , and was surprised at the 9.55° angle my calculation came up with.
Thanks for the picture! The approximated angle of 16.6 deg (coming from assuming a constant blade curvature, etc.) is not too far from your measured angle of around 14.5 deg. I would take your measured angle over any of our calculations any day of the week.
Not only that, many modern razors hide the blade from optical view, so a physical measurement is the only simple way to get a repeat reading.
There actually is another way to get that blade into the optical view. I used a modified blade to do that with my photo analysis of the Bevel:
Bevel DE Safety Razor: Review, Photos, Measurements, Photo Analysis
Summary The Bevel double-edge (DE) safety razor can be found in Target stores. It comes nicely packaged and has a fine appearance, but surface imperfections indicate that the razor is not made with the highest standards of quality. General measurements were made of the Bevel without a blade...
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