08-25-2019, 06:22 PM
(This post was last modified: 08-26-2019, 06:23 AM by KnifeGrinders.)
Differentiation between keenness and sharpness has been best done by Todd Simpson:
Keenness is measured at the very apex of the edge, while Sharpness is determined by thinness of the edge behind the apex, and depends on the edge angle.
https://scienceofsharp.wordpress.com/201...-and-keen/
https://scienceofsharp.wordpress.com/201...en-part-2/
The BESS test line is severed in the test by combination of a cut and tear.
The test line is about 200 micron in diameter; to cut it the edge has to go through at least a quarter of that, i.e. at least 50 micron, where the tear starts developing, and the test line eventually gets severed.
Owing to this, the BESS score that we see on the instrument reflects both the keenness and sharpness of the edge.
We know by experience that a higher angle edge, e.g. 40 degrees included, scores worse on the BESS Edge Sharpness Tester than a lower edge angle, e.g. 20 degrees included, even when the edge apex in both splits hair, i.e. the keenness is the same. This difference in the BESS score is due to the "sharpness" component of the testing.
There are 3 testers in the world that quantify sharpness: the US BESS Edge Sharpness Tester for $179-259, the New Zealand Anago for approx. $20,000, and the UK CATRA for approx. $50,000 - 80,000. For a small-scale sharpener the BESS Edge Sharpness Tester is the only feasible. Only a few of the larger knife making factories use the CATRA testing, while the Anago is used by some makers of the industrial knife sharpening equipment.
Of all 3, only the BESS Edge Sharpness Tester tests both the keenness and sharpness, and can tell about sharpness in the razor range.
CATRA can not be used to evaluate the edge sharpness, because the edge is abraded beyond shaving sharp in its 1st cycle, the edge gets practically dull by the 4th cycle (can't cut print paper), and the full test includes 60 cycles. CATRA best evaluates role of the blade geometry and the steel wear resistance in the cutting ability.
The NZ Anago evaluates the edge sharpness, but not the keenness.
Keenness is measured at the very apex of the edge, while Sharpness is determined by thinness of the edge behind the apex, and depends on the edge angle.
https://scienceofsharp.wordpress.com/201...-and-keen/
https://scienceofsharp.wordpress.com/201...en-part-2/
The BESS test line is severed in the test by combination of a cut and tear.
The test line is about 200 micron in diameter; to cut it the edge has to go through at least a quarter of that, i.e. at least 50 micron, where the tear starts developing, and the test line eventually gets severed.
Owing to this, the BESS score that we see on the instrument reflects both the keenness and sharpness of the edge.
We know by experience that a higher angle edge, e.g. 40 degrees included, scores worse on the BESS Edge Sharpness Tester than a lower edge angle, e.g. 20 degrees included, even when the edge apex in both splits hair, i.e. the keenness is the same. This difference in the BESS score is due to the "sharpness" component of the testing.
There are 3 testers in the world that quantify sharpness: the US BESS Edge Sharpness Tester for $179-259, the New Zealand Anago for approx. $20,000, and the UK CATRA for approx. $50,000 - 80,000. For a small-scale sharpener the BESS Edge Sharpness Tester is the only feasible. Only a few of the larger knife making factories use the CATRA testing, while the Anago is used by some makers of the industrial knife sharpening equipment.
Of all 3, only the BESS Edge Sharpness Tester tests both the keenness and sharpness, and can tell about sharpness in the razor range.
CATRA can not be used to evaluate the edge sharpness, because the edge is abraded beyond shaving sharp in its 1st cycle, the edge gets practically dull by the 4th cycle (can't cut print paper), and the full test includes 60 cycles. CATRA best evaluates role of the blade geometry and the steel wear resistance in the cutting ability.
The NZ Anago evaluates the edge sharpness, but not the keenness.
http://knifeGrinders.com.au