08-30-2019, 02:38 AM
(08-29-2019, 11:45 AM)EOU Wrote: It would seem that this might resonate with some of our members. It's an excerpt from a more extensive piece and authored by Keith Johnson with Tomo Nagura.
About sharpness – most people regard edge width to be the main critical concern where sharpness is concerned. To a lesser degree, the topography of the edge’s apex can be a factor also. It can be smoother or toothier, and that can aid or distract from its cutting ability. But at the end of the day, width of the edge is the common denominator that must be factored in first and most heavily. Edge width is controlled by bevel angle and only bevel angle.
So - are we to take from Keith that the final arbiter of "sharpness" will be determined by the bevel angle because smaller sharpening angles produce narrower edge apexes or are we to assume that when smaller angles are utilized the sharpness is improved due to improved geometries of the edge?
In my understanding the quoted text oversimplifies the situation. There is no doubt that the bevel angle is of major importance, but for complex understanding we have to include steel properties also. The way how the blade was ground is important also.
In my thinking the quoted text was written to describe the specific situation to straight razors, where the included bevel angle is mostly in the interval 17 to 19⁰. During honing this angle is fixed by the spine thickness and blade width.
If it is true that the quoted text was intended to straight razors, which are very shallow cutting tools, than it is not simply transferable to knives, whose behaviour is influenced also by cleaving and displacing the material far behind the edge.
Jan