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Weight On a String sharpness test
Thinking of ways to quantify or measure sharpness, I came up with this contraption. I have not actually built it yet.
Basically it is a weight on a string and a razor, all held on a plank. The plank is pivoted. The razor is held stationary in relation to the plank to prevent scraping action on the string.
As the plank is turned, the pressure of the razor on the string will increase. At some point, the razor will cut the string. That location is recorded and used as a measure of the blade's sharpness.
The test will have to be calibrated for that particular string, weight and geometry, but after that should be fairly consistent.
A good consistent string that somewhat resembles human hair may or may not be a mono-filament fishing line.
This test could be useful to compare sharpness between different razors. Or use the same razor to compare different stones or honing techniques. The test is less subjective than some of the other sharpness tests.
YMMV