Comment on Wednesday SOTD Thread - October 9th, 2024 (#486)
gcgallant@sub.wetshaving.social 3 weeks agoBtw, I determine the bevel angle by just calculating the sharpening angle and doubling it. On all the razors I’ve seen, the sharpening angle falls well within the range where the small angle approximation for sine works. Typically, I just do the trig in my head.
Once I started paying attention to sharpening geometry, I started to realize why I like certain razors so much. I would be very interested in your experience on this as well. I’ve realized the ways in which I adapt to razors with wider bevel angles and this tips me off to actually measure them.
djundjila@sub.wetshaving.social 3 weeks ago
I’m not sure I follow. I’d have just measured the spine thickness t at the place of hone wear, and the width b from edge to spine hone wear and computed the bevel angle as α= 2 arc sin(b/(2w)), just as the central angle of an isosceles triangle . Is the sharpening angle β = α/2? in that case, I agree that β ≈ sin(β), certainly at the precision I’ll have measuring t, and b.
gcgallant@sub.wetshaving.social 3 weeks ago
Yes, that’s the sharpening angle. The bevel is formed by laying the razor on the stone at the spine and edge. The razor is sharpened by removing material (abrading) until the centerline from the spine through the edge intersects with the stone’s surface. For a razor, that angle is typically less than ten degrees and within the small angle approximation range. If I have my phone handy, I just use the calculator. Much more convenient than a slide rule :)
djundjila@wetshaving.social 3 weeks ago
For the approximation to become useful, we just need to start thinking of bevel angles in units of radians now 😄
gcgallant@sub.wetshaving.social 3 weeks ago
Already there, except I think in terms of sharpening angle and save the multiplication step. Since you have a penchant for maths, you’ll be soon to follow :)