Edge Structual Weakness - Plastic Crushes Steel

[KnifeGrinders]

it is an interesting situation. DE razor blade edges don't dent, microtome edges don't dent and knife edges that measure 25 don't dent. If these edges did dent then these edges would measure much higher than 25 or 50...
We can say that the presence of burr (or a  wire edge) often plays a key role here but only with edges that are structurally weak to begin with. When the burr folds over the structurally weak edge, several hundred grams of force may now be applied to the edge. If the underlying material is weak, it may dent. It's not difficult to detect a dented edge, they measure from 600 to maxing out the BESS scale.

This structural weakness in the edge must be caused by Burnishing.
The way I finish our edges, edge-trailing on paper wheels, goes with burnishing, dragging metal from bevels over the edge apex.
When the knife is of a quality steel I get sharpness testing <= 50, but when it is a lower-end budget/junk knife it tests as Mike describes.

For example, a cheap knife sharpness scores. The edge was set on #400 at 14 dps, and then deburred on 2 paper wheels - one with a 5 micron diamond paste at a higher angle of 15.6 dps, followed by a paper wheel with 0.5 micron diamonds at the exact edge angle of 14 dps.

Off the #400 (visible burr) = 555 BESS
Paper wheel 5 mcrn @ +1.6 degree higher twice, alternating sides = 165 BESS
Paper wheel 0.5 mcrn @ exact edge angle once, alternating sides = 495 BESS (visible dent)
Paper wheel 5 mcrn @ +1.6 degree higher twice, alternating sides = 125 BESS
Paper wheel 0.5 mcrn @ exact edge angle, alternating sides: once = 330 BESS; twice = 700 BESS (visible dent)

Apparently, in honing at the exact edge angle burnishing creates the structurally weak edge apex that then behaves as Mike has described, i.e. folds allowing to apply more force against the test line to crush and dent. While the high-angle finish allows to get a stable shaving edge.

Todd Simpson on his scienceofsharp.wordpress.com has shown by SEM that straight razors finished edge-trailing on a strop with 0.5 micron diamonds invariably get a wire edge. Todd recommends to finish straight razors by high-angle stropping on a hanging strop with a metal polish (they commonly have abrasive particles of 3-6 microns in size).

This reminds me of the Mutant Burr thread - that  was observed by Grepper when manually stropping on a leather strop; nowadays Grepper strops on a leather or cotton belt on a belt grinder, and the burnishing effect should be more pronounced.

Paper wheel or belt grinder stropping drags enough metal from bevels over the apex to overlay a new extra-thin edge.
This edge will split a hair, but in cheap stainless steel blades will not hold a load.
This edge is also prone to the post-sharpening loss of sharpness discussed in the neighboring thread

We've been hashing these phenomena long enough to see the two contributing factors that play role in each: the stressed edge apex we create when sharpening, and the weak ultra-edge we create by burnishing when deburring.

The wire or foil edge created by burnishing has properties different from the underlying edge, it resembles the unhardened steel in behaviour and in how it tests on the sharpness tester.