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- Sep 19, 2001
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A year ago, I ordered some steel, had it laser cut to shape, heat treated by a commercial provider, hollow ground on automated liquid cooled grinders, finish ground by a professional knifemaker, sharpened by a professional sharpener, and eventually tested on a CATRA knife edge tester with their ISO standard. 16 blades were cut. The steel was from the same manufacturer, shipped from the same distributor, blanked on the same machine, heat treated at the same location, ground on the same equipment, sharpened by the same person with the same equipment, tested on the same machine, and tested within one 48 period. The rockwell hardness was tested and the edge angles measured with a laser goniometer.
I'm not going to post all the cut numbers and all the test runs, as there were many, and the combinations of runs varies depending on which factor is being compared. Three runs could not be used due to an error in the process resulting in three blades being sharpened at an incorrect angle.
Heat treat - non-cryo performed best on 68% of the runs, averaging 9.7% more media cut. For the runs the cryo blades performed best at, the results averaged 6.5% better. This test was of only one method of cryo treatment. All I can surmise is that short soaks, even at -300F, is not beneficial, and in fact reduced cutting performance of the high carbon stainless. Other tests have shown cryo treated high alloy steels to have improved wear resistance, but I would suggest that if you want a cryo treated blade, request the soak to be overnight or longer. I cannot say it will improve the blade, but this test suggests that short soaks can do the opposite.
Steel manufacture - Particle metallurgy bested ingot cast in 80% of the test runs. The PM version of the same alloy content out cut the ingot cast by an average margin of 13.5% more media, while the runs in which ingot cast came out ahead was by 7% on average. Since all the blades have the same alloy content, they all received the same cryo/non-cryo heat treats. The PM version had a slightly better heat treat response, as the PM blades were 0.5 to 1 point harder than the ingot cast versions. It cannot be said that simply being PM made the blades cut more media, as it could be the difference in hardness, and the ingot cast could have been heat treated to gain that extra point. But, from a practical standpoint, the same heat treat for both versions wound up with a harder, longer cutting blade, which is also reportedly more impact resistant than the ingot cast version.
Primary grind - The thinner ground blades cut longest in 85% of the runs, leading by an average 21% more media cut. The thicker blades (twice the thickness, but still only half a mm before sharpening) led by 5% on average for the few runs it came out ahead. Even sharpened to the same final edge angle, this comparison shows that the thinner initial grind provides a very noticeable change in edge life in slicing. This may complicate comparisons of alloys if using different knives from different manufacturers. Even with an Edgepro/Wicked Edge/Aligner, the matching angle can still not match performance due to the knife being thicker behind the edge.
Edge angle - This played the largest role in edge life measured by amount of media cut. A 34 degree inclusive edge outcut a 50 degree inclusive edge by about 2.7 times. Total media cut numbers for the 50 degree inclusive edges were very low in comparison, with some test runs of the 34 degree edges cutting more media than the 50 degree edges in one-twentieth as many cutting strokes. Dropping from 34 to 27 degrees included produced an average improvement of 1.4 times, again still larger than any of the other measured variables.
Edge polish - Sharpening was done with a jig to maintain consistent angles, on monocrystalline diamond, and checked with a laser goniometer. Not very large differences, quite in line with the other factors except for edge angle. For the slicing cut against silica bearing paper, 25 micron edges did best 71% of the runs, 3 micron took second place in 57% of the runs, and 45 micron was last in 71% of the runs. I did not compare each combination of grits, but did find that for the average difference between first place finishers (most often 25 micron, but not always) and second place (again, 3 micron just more than half) was 4.5%. From first to third (most often 45 micron) was 12% on average.
This testing had nothing to do with impact toughness, corrosion resistance, cost, appearance, etc. No push cutting performance was tested. No manila rope or cardboard was cut. The blades were not stressed laterally or struck with/against any objects. The blades have no handles/ergonomic factors, are not for sale commercially, and will not be compared to knives either production or custom.
I am still evaluating the results and will try to generate a paper with the actual test procedure, more material property measurements, visual inspection of edge condition, references to published papers on edge retention and cutting forces, and hopefully some extra analysis of the numbers, including first cut performance and edge degradation pattern.
I'm not going to post all the cut numbers and all the test runs, as there were many, and the combinations of runs varies depending on which factor is being compared. Three runs could not be used due to an error in the process resulting in three blades being sharpened at an incorrect angle.
Heat treat - non-cryo performed best on 68% of the runs, averaging 9.7% more media cut. For the runs the cryo blades performed best at, the results averaged 6.5% better. This test was of only one method of cryo treatment. All I can surmise is that short soaks, even at -300F, is not beneficial, and in fact reduced cutting performance of the high carbon stainless. Other tests have shown cryo treated high alloy steels to have improved wear resistance, but I would suggest that if you want a cryo treated blade, request the soak to be overnight or longer. I cannot say it will improve the blade, but this test suggests that short soaks can do the opposite.
Steel manufacture - Particle metallurgy bested ingot cast in 80% of the test runs. The PM version of the same alloy content out cut the ingot cast by an average margin of 13.5% more media, while the runs in which ingot cast came out ahead was by 7% on average. Since all the blades have the same alloy content, they all received the same cryo/non-cryo heat treats. The PM version had a slightly better heat treat response, as the PM blades were 0.5 to 1 point harder than the ingot cast versions. It cannot be said that simply being PM made the blades cut more media, as it could be the difference in hardness, and the ingot cast could have been heat treated to gain that extra point. But, from a practical standpoint, the same heat treat for both versions wound up with a harder, longer cutting blade, which is also reportedly more impact resistant than the ingot cast version.
Primary grind - The thinner ground blades cut longest in 85% of the runs, leading by an average 21% more media cut. The thicker blades (twice the thickness, but still only half a mm before sharpening) led by 5% on average for the few runs it came out ahead. Even sharpened to the same final edge angle, this comparison shows that the thinner initial grind provides a very noticeable change in edge life in slicing. This may complicate comparisons of alloys if using different knives from different manufacturers. Even with an Edgepro/Wicked Edge/Aligner, the matching angle can still not match performance due to the knife being thicker behind the edge.
Edge angle - This played the largest role in edge life measured by amount of media cut. A 34 degree inclusive edge outcut a 50 degree inclusive edge by about 2.7 times. Total media cut numbers for the 50 degree inclusive edges were very low in comparison, with some test runs of the 34 degree edges cutting more media than the 50 degree edges in one-twentieth as many cutting strokes. Dropping from 34 to 27 degrees included produced an average improvement of 1.4 times, again still larger than any of the other measured variables.
Edge polish - Sharpening was done with a jig to maintain consistent angles, on monocrystalline diamond, and checked with a laser goniometer. Not very large differences, quite in line with the other factors except for edge angle. For the slicing cut against silica bearing paper, 25 micron edges did best 71% of the runs, 3 micron took second place in 57% of the runs, and 45 micron was last in 71% of the runs. I did not compare each combination of grits, but did find that for the average difference between first place finishers (most often 25 micron, but not always) and second place (again, 3 micron just more than half) was 4.5%. From first to third (most often 45 micron) was 12% on average.
This testing had nothing to do with impact toughness, corrosion resistance, cost, appearance, etc. No push cutting performance was tested. No manila rope or cardboard was cut. The blades were not stressed laterally or struck with/against any objects. The blades have no handles/ergonomic factors, are not for sale commercially, and will not be compared to knives either production or custom.
I am still evaluating the results and will try to generate a paper with the actual test procedure, more material property measurements, visual inspection of edge condition, references to published papers on edge retention and cutting forces, and hopefully some extra analysis of the numbers, including first cut performance and edge degradation pattern.
