My question is this, has any one devised a home cutting test on two blades, prepared , heat treated , profiled , sharpened as identical as possible and then put them to a cutting test to compare cryo to not cryo treated?
Ken
I have done exactly that. Because of the way I make my knives (I mill them), I'm able to get my test blades very similar.
D2, at higher hardness, lower tempers, retains a
lot of austenite. Depending on your austenitizing times and temp, upwards of 15%
D2, without cryo (or with cryo and too much of a snap temper) suffers miserable edge roll. Someone unfamiliar with the hardening characteristics of D2 might think it has pearlite in it or something, it rolls so bad. I have not been able to do D2 at high harness without this problem, and the only way I know to address it is cryo. And the difference cryo makes is huge, in this steel in this condition.
My cutting test uses three knives and three test media. I use a standard blade I always include in the test every time I do it, the new test blade, and one of a few high end production knives, such as a Chris Reeves, with similar geometry. I sharpen all three knives to the same angle and level of sharpness.
The first test is to cut an identical amount of the same cardboard with three knives. Normally about 150 inches of cardboard per knife. I then clean the fuzz off the edges and view all three side by side under magnification and strong light. You would be surprised how much visible wear a blade can sustain and still shave hair. I am not attempting to measure the wear, I'm compairing them against each other.
The second test is similar to the first except I cut thick leather - which is very abrasive. These two tests tell me a lot about how the edge is going to perform in the real world.
The last test is whittling cuts in a very hard hardwood. I take one cut, per blade, five times, to try spread out some of random variation in my technique. This isn't extremely scientific, but I can get fairly reproducible results this way.
In conclusion:
Using this test, in nearly identical test samples that even measure the same Rockwell hardness, cryo in D2 heat treated the way I do, improves edge retention in the abrasive media a noticeable amount, and improves edge stability in the hardwood component enough that the part with cryo is dull, but the part without cryo has edge damage visible while viewing the blade with an outstretched hand. The difference is huge and I could not, in good conscious, sell a D2 blade at this hardness without cryo. Higher tempering temps decompose the RA, so it becomes moot, but higher tempers has another set of issues.
My test does not attempt to quantify dullness. It is a comparison test against known constants, the results being either better than, or not as good. They have been for my own use in refining my knives and were never intended to prove or disprove the effectiveness of cryo to my peers. But the refinement in my process from this testing does give me enough confidence in my HT and in D2 to make the claim that it will outperform all production knives in my test that I have tested to date, and that includes some big name production knives and some fancy steels. D2 is good stuff, and for me - cryo is an importaint part of making it work.
) However, it tolerates more yanking in a vice to break the tip off, for what that is worth. The edge stability on the softer D2 is so poor it will not hold an edge well when sharpened more acute than about 20 per side. Or, perhaps I'm just doing it wrong.
