11-18-2017, 12:56 PM
FWIW, I’ll chime in.
Like you mentioned, I too think there are a number of factors that contribute to sharpness variation along the edge.
Belts act a bit differently than stones because there is some wrap around of the belt as it deflects around the bevel. It makes sense that once the edge is ground sharp, if on one pass over the belt the sharpening angle is a little steeper (less acute), that pass actually grinds a new edge. If the pass is less acute, the edge is not ground as much or not at all. If the sharpening angle varies, then different areas along the edge are not ground evenly.
I know that I cannot exactly consistently maintain exactly the same angle between passes or even over the length of the blade when doing it by hand no matter how careful I am. Hence I use a knife rest. Personally, I get sharper edges with more consistent sharpness along the edge using a rest than when I attempt to do it by hand.
With a rest I can produce a nice even burr along the entire edge. It seems to me that if the burr is not even along the edge, or if some areas have a burr and some don’t, that the edge is not evenly sharpened.
Another thing that seems to work for me is to use very light pressure. When I sharpen there is almost no belt deflection and the blade does not get warm. I suspect that this minimizes variation with each pass. Imagine if you sharpen with light pressure on one part of the blade and then really get into the belt on another. Obviously, the blade won’t be evenly ground. Light pressure also produces less burr and the burr is not as tough.
Of course there are other factors such as burr and toothy/smooth, etc., but maintaining a consistent sharpening angle and even pressure goes a long way in minimizing sharpness variation along the edge. Consistency is the key.
It makes sense to me too that if an edge is ground evenly and at the same angle, that the apex width will be the same along the edge and therefore will have less sharpness variation.
Anyway, that seems to work for me, and is what I think is going on.
Like you mentioned, I too think there are a number of factors that contribute to sharpness variation along the edge.
Belts act a bit differently than stones because there is some wrap around of the belt as it deflects around the bevel. It makes sense that once the edge is ground sharp, if on one pass over the belt the sharpening angle is a little steeper (less acute), that pass actually grinds a new edge. If the pass is less acute, the edge is not ground as much or not at all. If the sharpening angle varies, then different areas along the edge are not ground evenly.
I know that I cannot exactly consistently maintain exactly the same angle between passes or even over the length of the blade when doing it by hand no matter how careful I am. Hence I use a knife rest. Personally, I get sharper edges with more consistent sharpness along the edge using a rest than when I attempt to do it by hand.
With a rest I can produce a nice even burr along the entire edge. It seems to me that if the burr is not even along the edge, or if some areas have a burr and some don’t, that the edge is not evenly sharpened.
Another thing that seems to work for me is to use very light pressure. When I sharpen there is almost no belt deflection and the blade does not get warm. I suspect that this minimizes variation with each pass. Imagine if you sharpen with light pressure on one part of the blade and then really get into the belt on another. Obviously, the blade won’t be evenly ground. Light pressure also produces less burr and the burr is not as tough.
Of course there are other factors such as burr and toothy/smooth, etc., but maintaining a consistent sharpening angle and even pressure goes a long way in minimizing sharpness variation along the edge. Consistency is the key.
It makes sense to me too that if an edge is ground evenly and at the same angle, that the apex width will be the same along the edge and therefore will have less sharpness variation.
Anyway, that seems to work for me, and is what I think is going on.