05-14-2018, 09:08 PM
(This post was last modified: 06-23-2018, 10:37 PM by KnifeGrinders.)
The "proper sharpness" discussion obviously comes from the common observation that thinner edges roll from heavy use.
Firstly, shall we not confuse over-thinned vs properly angled edge with sharpness as such.
Secondly, shall we not confuse toothy vs polished edge with sharpness as such.
Then look at this 'proper sharpness' through Cliff Stamp's "thinnest possible edge for the task" and our experimental data that the best stability to rolling has the lowest possible angle for the steel with the best initial sharpness - and you immediately see that the whole 'proper sharpness' and 'sharpness for the task' concept is untenable.
Sharpness shall always be the best achievable for the given steel sharpened at the acutest angle fitting the task. We do not "sharpen for the task" - we "angle for the task", and angled for the task edge should be sharpened to the sharpest apex you can.
Mike B. has helped me visualize why the sharpest edge is always to the good:
try seeing the rolled edge with your mental vision, see this edge bend and the sharp apex at its end - the stuff it cuts wraps over the bend until it contacts the edge apex where it is severed; when the apex is sharper even the rolled edge cuts with better efficiency. In other words, the sharper edge mitigates edge rolling.
Sharp apex does not predispose the edge to rolling - over-thinning the edge past the angle at which it deforms in cutting certain stuff does.
We could have remembered that a properly sharpened felling axe must shave, to see that the 'proper sharpness' concept is untenable.
"Always check the ax for sharpness... If you followed procedures, your edge should be sharp enough to shave with." Page 31 of the An Ax to Grind. A Practical Ax Manual.
Firstly, shall we not confuse over-thinned vs properly angled edge with sharpness as such.
Secondly, shall we not confuse toothy vs polished edge with sharpness as such.
Then look at this 'proper sharpness' through Cliff Stamp's "thinnest possible edge for the task" and our experimental data that the best stability to rolling has the lowest possible angle for the steel with the best initial sharpness - and you immediately see that the whole 'proper sharpness' and 'sharpness for the task' concept is untenable.
Sharpness shall always be the best achievable for the given steel sharpened at the acutest angle fitting the task. We do not "sharpen for the task" - we "angle for the task", and angled for the task edge should be sharpened to the sharpest apex you can.
Mike B. has helped me visualize why the sharpest edge is always to the good:
try seeing the rolled edge with your mental vision, see this edge bend and the sharp apex at its end - the stuff it cuts wraps over the bend until it contacts the edge apex where it is severed; when the apex is sharper even the rolled edge cuts with better efficiency. In other words, the sharper edge mitigates edge rolling.
Sharp apex does not predispose the edge to rolling - over-thinning the edge past the angle at which it deforms in cutting certain stuff does.
We could have remembered that a properly sharpened felling axe must shave, to see that the 'proper sharpness' concept is untenable.
"Always check the ax for sharpness... If you followed procedures, your edge should be sharp enough to shave with." Page 31 of the An Ax to Grind. A Practical Ax Manual.
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