06-06-2021, 12:18 PM
Hello friends.
As a new member, I am trying to get up to speed with the rest of you as quickly as I can, so that I don’t bother you with unnecessarily dumb questions.
So, having found this ancient thread that goes almost back to the beginning of BESS time, maybe a comment or two might bring us up to closer to the present…………………
The main points of interest in this thread – at least to me – are that sharpness (measured by BESS) worsens over night, but can be brought back by either the passage of time, or by stropping.
Some of us are wondering is “metal memory” exists, and what it has to do with our problems of “edging on up.”
Having worked years ago with sheet metal, I am familiar with the concept of “springback,” which is when you bend a piece of metal a certain amount, and it “springsback” some.
Bend that metal too far, and it will never recover.
https://www.thefabricator.com/thefabrica...ingforward
One wonders if this is happening with our edges…….
There might also be the consideration of "Coefficient of restitution," where we "impact" our metal blades at the microscopic level, and that induces stress to the edge.
https://www.scienceabc.com/pure-sciences/coefficient-of-restitution-definition-explanation-and-formula.html
Another consideration might be that with vigorous stropping, we are “locally heating” our VERY fine edge above the annealing temperature of the metal at the edge – leaving a softer metal that is less good at edge holding.
When I was making knives, I was very careful with grinding after tempering. Bare hand on the blade close to the grinder, and quick dunks in the water at every opportunity. Sometimes I could see “color” in the edge without ever feeling the heat in the blade. Local heating.
Afterwards, stropping eliminated the “micro-softened” metal, and then a return to a hard edge.
Combined with eliminating the “metal fatigued” edge left by the “metal memory” rough treatment, we can then strop to an edge better than originally formed.
Remember that springs in general are an easy example of "metal memory."
But they too eventually wear out or get damaged.
As a new member, I am trying to get up to speed with the rest of you as quickly as I can, so that I don’t bother you with unnecessarily dumb questions.
So, having found this ancient thread that goes almost back to the beginning of BESS time, maybe a comment or two might bring us up to closer to the present…………………
The main points of interest in this thread – at least to me – are that sharpness (measured by BESS) worsens over night, but can be brought back by either the passage of time, or by stropping.
Some of us are wondering is “metal memory” exists, and what it has to do with our problems of “edging on up.”
Having worked years ago with sheet metal, I am familiar with the concept of “springback,” which is when you bend a piece of metal a certain amount, and it “springsback” some.
Bend that metal too far, and it will never recover.
https://www.thefabricator.com/thefabrica...ingforward
One wonders if this is happening with our edges…….
There might also be the consideration of "Coefficient of restitution," where we "impact" our metal blades at the microscopic level, and that induces stress to the edge.
https://www.scienceabc.com/pure-sciences/coefficient-of-restitution-definition-explanation-and-formula.html
Another consideration might be that with vigorous stropping, we are “locally heating” our VERY fine edge above the annealing temperature of the metal at the edge – leaving a softer metal that is less good at edge holding.
When I was making knives, I was very careful with grinding after tempering. Bare hand on the blade close to the grinder, and quick dunks in the water at every opportunity. Sometimes I could see “color” in the edge without ever feeling the heat in the blade. Local heating.
Afterwards, stropping eliminated the “micro-softened” metal, and then a return to a hard edge.
Combined with eliminating the “metal fatigued” edge left by the “metal memory” rough treatment, we can then strop to an edge better than originally formed.
Remember that springs in general are an easy example of "metal memory."
But they too eventually wear out or get damaged.