...constructive criticism?
TCE: how much material cut before testing for dullness in what manner? Did it vary at all? In Jim's tests, blades start at 15-dps with same edge finish and cut until 20-lbs cutting force is achieved, i.e. an end-point. This is stated in the model. TCE distracts from the model, allows for variation in sharpness testing and when sharpness was tested, i.e. no defined end-point.
Too much focus on a hypothetical apex "angle" rather than
thickness. The apex-thickness of a felling axe increases substantially in use compared to a knife, but a narrow apex isn't as important as a narrow bevel on a felling axe, i.e. it doesn't need to be shaving or paper-slicing sharp to penetrate. To wit, the working apex-angle of a felling axe is ~45-dps, resharpening is aimed at reducing the bevel shoulders somewhat but maintaining sufficient thickness
behind the edge to prevent the metal from deforming and fracturing with repeated strikes. That thickness is MUCH higher than the knives being compared, and the
primary bevel angle of an axe is >10-dps. For a knife, it is <5 dps, MUCH thinner (like his early graphic). A perfectly sharpened steel apex is still ~45-dps, 0.1-0.5 um thick, that is the best steel can do. BEHIND that apex you can have a bevel angle. But even steels of the finest grain can't maintain 5-dps from an apex 0.5um thick through much use, it is just too thin, rolls/deform/tears/cracks, which is why 15-20 dps remains the recommended apex angle (i.e. micro-bevel) for everything from fine kitchen cutlery to wood-chippers. 15-dps means that the steel is 2x taller than it is thick via cross-section. When you bring your edge lower than this, there's a good chance you'll actually end up with a thicker apex diameter than you'd have at a higher angle. For highest initial sharpness, that diameter, that thickness, is what matters. The question is
how thin to bring the blade behind this 15-dps bevel. 0.015"? 0.010? 0.005? Note than reducing the edge thickness by half may improve penetration by 2-4x but reduces edge-stiffness (i.e. resistance to deformation that can lead to fracture) by ~
8-fold. The thinner you go, the weaker and more specialized the blade.
The problem is that utility work OFTEN involves lateral loads and impacts on hard materials. We are more worried about our tools
breaking, our edges going flat or chipping-out than we are about the abrading away because those are the ways we most often encounter dullness. Before we worry about abrasion resistance, we worry about the strength of the tool itself. Abrasion resistance is a lower priority than edge strength. But at 15-dps and 58+Rc, edge-strength among knives becomes fairly set, you need only establish a working edge-thickness for what type of cutting you expect to do. Once that is established, the high wear steels offer increased abrasion resistance for those who want/need it without sacrificing much strength/toughness.
How does that relate to low-wear steels like CTS-BD1? At the same geometry, BD1 abrades away more quickly to dullness. You can take the blade down to an angle that thins out the blade to a more narrow microbevel, essentially thinning a back-bevel. Using this thinner geometry, you can maintain a higher cutting efficiency through abrasive wear for longer. Your apex is just as dull, dulls just as quickly, but the bevel shoulders are thinner so they incur less resistance than a thicker geometry - less wedging-force = less resistance to continued cutting = higher apparent wear-resistance. Just don't use it like you would a high-wear blade with thicker geometry, i.e. subject it to the same levels of stress, or your new found abrasion-resistance will be lost to the more common concerns of blade strength. Unless you need to do a lot of abrasive cutting, i.e. the task those high-wear steels were designed to meet... you might as well use it at the same geometry you would use any other knife that you'd subject to the stresses you ted to encounter. OR you could thin it out to compete with high-wear steels and see if Cliff is right. *shrug*
