It shouldn't be that hard to make an equation which could give a 'slicey-ness' number. Factoring in BTE thickness, spine thickness and blade height. Plug in a few well known slicey and non slicey blades to establish benchmarks and you now have a way to compare slicing performance. I realise it would only be effective for FFG blades, other grinds would throw a spanner in the equation.
Now if only I was mathematical.
Cutting is a combination of edge-strength (and
stiffness) and
mechanical advantage. The latter is what you mean by "slicey-ness".
Beginning at the very apex of the edge, every edge ends at ~90' per-side, i.e. flat blunt (for any who think "tangent" is appropriate for establishing the edge-angle on convex edges, let that sink in). Microscopic measurements of edge-thickness at the apex are given an assumed
diameter, a small diameter = "sharper apex". However, the apex is only where the cutting begins, that apex must be pushed to some depth to complete a cut of material with thickness 'x'.
To maintain a straight cut, the material behind the very thin apex-diameter, i.e. the blade, must be sufficiently strong/stiff to withstand forces that could compress it or turn it aside. To resist compression, the blade may be made of very
hard material (perhaps measured by Rockwell). But to resist bending, the blade must be "
stiff" which is determined almost entirely by blade
thickness and indeed the relationship between stiffness and thickness is
cubic and can be simplified as such for our purposes. To maintain the
mechanical advantage in cutting, the blade must remain thin. Mechanical advantage for a wedge like a knife blade is calculated simply as the ratio of the "slope length" to the maximum
thickness of the amount of blade inserted into the cut. If we were to plot these values relative to
edge angle (I used degrees-per-side), we can visualize the different profiles of knife edges as seen below. You will note that I described the mechanical advantage as "cutting efficiency" and resistance to side-bending as "strength" which is not entirely accurate but is more colloquial.
While these charts describe first-and-foremost the edge-bevel of a blade, they can also be used to describe the primary bevel. To make sure we are on the same page, it must be understood that the "primary bevel" describes the main bevel of the blade, usually ground before a secondary or edge-bevel that establishes the final geometry leading to the apex.
On most knives, that secondary bevel should be very very small, as small as is required to achieve sufficient durability at the edge. Most chainsaws, axes, chisels, planes, and knives of all sorts recommend an edge bevel ~15' per side or 30'-inclusive to maintain sufficient durability, but this of course depends on your use. You can see where 15-dps falls in the charts above.
For the primary bevel behind that edge, "strength" and "cutting efficiency" only matter once the cut has progressed deep enough to reach that section. Here, the blade usually continues to get thicker although this can be mitigated in large part by a very thin or even hollow (concave) grind that keeps the cutting efficiency as high as possible (why Bucks are often amazing slicers). In most knives, the primary bevel averages <5-dps.
I hope this is helpful to y'all.
ETA: "Slicey-ness" of a blade with bevel-angle X = 1/(2*Tangent(X)) Please note, this comparison assumes the same blade height at the measured thickness or angle. If comparing knives with different blade-height, the taller blade is disadvantaged if the depth of the cut progresses beyond the height of the shorter blade.
Also please note that this calculation takes no account of frictional forces encountered with increasing wedge-thickness or with various surface features of a blade that may increase the force required to complete a cut. The reduced friction of a smooth bevel may outweigh differences in geometry compared to a thinner blade with a very rough grind.
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