GarageBoy wrote: ↑
Wed Sep 11, 2019 6:14 am
Curious - how low of an angle will these 3 steels hold and not chip out for normal edc tasks (reliably) ?
It really depends on what 'normal use' is for that individual user. For example, cutting through cardboard really fast will increase impact damage from hard particle inclusions, compared to slicing it slowly. Slamming a knife into a bamboo chopping board repeatedly while slicing vegies will be harder on the edge than cutting the same material smoothly on an end grain board.
So I don't really like to give prescriptive angles and thicknesses. The way to find what the thinnest, most acute edge is for you, is just to keep thinning it out until it starts to fail by chipping or rolling in normal use, then gradually increase your angle little by little until it stabilises for you.
There you will have your individually customised 'lowest edge angle'.
Having said that, some of my Japanese chef knives are around 0.006" behind the edge, and sharpened at around 8 degrees per side. That's VG10 and White Paper No.1 steel, but HAP40 can no doubt handle the same. ZDP189 is also commonly used in Japanese chef knives, so it can probably take a similar angle and thickness, although I've never personally examined a chef knife in either steel.
When K390 was first released, I remember someone asking the Bohler metallurgists whether it would be able to be used to make custom straight razors. I was a bit dubious, considering the carbide volume, but they seemed to think it would perform very well in a straight razor.
Straight razors tend to be around 16 degrees inclusive.
Those kind of edges are obviously not really suited for most 'utility use'.