But youtubers are focusing on hrc and not realizing that hrc only shows hardness (at the tang or whatever flat surface was tested on the blade and only on the surface of where it was tested). It doesn't show grain size, not RA, not crystal structure etc. Things that matter more than hrc. The other thing would be geometry supporting that heat treatment for performance.
Mo2
, forgive me if it seems I’m saying things you might already know, but I feel obliged to provide clarity or specificity for observers who may not.
I can’t speak for everyone, but I
can speak for Supersteel Steve, Gerald from Outpost76, Kenny from InthePocket, and myself. The four of us talk every day, and routinely reference that hrc is not the be all, end all in videos.
There is also an asterisk to note.
Depending on the application and material being cut, different aspects of the steel will be emphasized to varying degrees in determining performance. This is a key piece to understand, and it’s the short explanation for why cardboard and rope test results look so different.
For example, Larrin’s equation for predicting CATRA results uses 3 primary drivers: edge angle (geometry), steel, hrc (effectively, matrix hardness). In this particular case, cutting 5% silica impregnated cardstock, raw hardness usually
outweighs the variance of grain size, distribution, etc that we’re likely to get if ht protocols are followed at least passably. Italics used there to note that it is possible for ht to be blown so badly that raw hrc would no longer overpower it in CATRA, but that is uncommon, which is why the equation works.
Cardboard testing is essentially a less controlled analog for CATRA, as cardboard is similar in composition to silica impregnated cardstock— silica is the primary abrasive here, as well. Steve, Gerald, and Tom Hosang each control edge angle and steel in their testing, allowing for consistency in 2/3 primary drivers, and results often vary as a result of heat treatment. An example that comes to mind is the CRK S35VN at 59hrc having out cut S30V and S35VN which were equal or a point higher in hrc, which has been observed in two samples, by two testers, with mirrored results (Steve and Tom).
In rope testing, your note about going beyond raw hrc really shines. Here, steel composition, grain size and distribution, etc overpower raw hrc consistently. M390 at 58hrc will consistently out perform S30V at 60hrc here, where they're likely to flip flop vs cardboard.
So, at least in reference to the group of us that I specified above, we do understand that hrc is just one piece of the puzzle. We’re also aware that in certain specific, very common/relevant applications, it’s a really, really big piece of the puzzle. In other applications, it takes a back seat.
