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+--- Thread: How I use my sharpness tester to improve sharpening (/showthread.php?tid=192)
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RE: How I use my sharpness tester to improve sharpening - Bud - 11-18-2017
KnifeGrinders you sound like a good person to ask this question. I just posted to another section of this forum with the guess that inconsistency in my grind angle (freehand on a Kally belt sander) is contributing to an inconsistency in edge tester readings along the length of a blade (as much as 40 - 50 points). I know it's not the edge tester or my technique because I've tested many different manufactured edges with almost perfect results. I realize that there could be other contributing factors (burr etc.) but do you feel that grind angle or pressure inconsistency alone could be a major problem?
I don't mean to limit this question to KnifeGrinders. If someone else has an opinion to I'd be glad to learn what you think.
RE: How I use my sharpness tester to improve sharpening - grepper - 11-18-2017
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.
RE: How I use my sharpness tester to improve sharpening - KnifeGrinders - 11-19-2017
My thoughts sing in unison with Grepper's.
What helped my understanding was when I questioned myself why knife grinders are so bothered to raise a nice even burr, when straight razor sharpeners do not.
Straight razor typical sharpening routine is similar to ours in major steps - they start with setting of the bevel with an abrasive in the 1000 grit range, BUT take extra care not to raise any burr, this is easily achieved with alternating x-strokes. Most then go straight to stropping; others may progress to grit #4000, or some freaks even up to 16K, then to stropping.
WHY knife sharpeners NEED to raise the burr by repeated abrasion of one side of the blade? - we just cannot get a sharp edge without raising a tiny and symmetrical burr on each side.
I won't be insulting intelligence of the forum fellows by giving direct answer, moreover that Grepper has given it above by at least 4/5th.
RE: How I use my sharpness tester to improve sharpening - Ken S - 11-19-2017
KG,
The very organized way you use BESS testing reminds me of how I did transmission noise tests on telephone lines. Back in the 70s, my foreman, knowing I was interested in such things, issued me a transmission noise meter. This testing was rare back then. I began testing every line I installed or repaired. Soon I developed a sense of when things were right or problematic, which stood by me throughout my career. The testing, like BESS testing took only a minute or two, and were both an excellent learning tool and documentation.
Keep up the good work. The Australian BESS agent will benefit greatly from it! (so will the rest of the globe.)
Ken
RE: How I use my sharpness tester to improve sharpening - grepper - 11-19-2017
I do what I can to keep burr formation to an absolute minimum. If there is any substantial burr, I do a few very light alternating side strokes to remove as much of it as possible before stropping. Once the blade is sharp, it only takes one light pass to raise a very small, even burr.
There is nothing inherently good about a burr. I use it just to indicate an even grind along the edge and try to keep it as small as possible along the way. Big heavy duty burrs can be almost impossible to remove by non-abrasive stropping. The key is to have as little burr as possible before stropping. If you don't do that, then it becomes necessary to use abrasive when stropping which will not only grind away the burr but also grind away the "toothy".
Burr removal on a polished edge is easy. Maintaining a toothy edge just requires a slightly different approach.
RE: How I use my sharpness tester to improve sharpening - Bud - 11-19-2017
Much appreciated gentlemen. I know that I am talking to a much more accomplished group of sharpeners than I am so thankful for the assistance. One way or the other I'm going to isolate and identify the issues. Edge testing helps in that regard greatly. I really appreciate as well what I have learned from Knifegrinders very detailed and informative previous posts. Thanks for the help to everyone!
