How do you sharpen for the best BESS score?

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Diemaker

Knifemaker / Craftsman / Service Provider
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I just ordered a PT50A and will soon be trying to get the best possible score for a competition. I would rather learn from others than have to do all of the mistakes myself, and figure others here may be curious about this themselves. I have done a few searches that have come up empty so if I missed something let me know. I would like to keep this thread about how to do it and omit whether it makes a useful edge or not, which for me I am betting is a no. Still, I want to see how keen I can get a useful edge too.

I expect this is a toy I will get bored with in a few months so may do a pass-around with it if there is interest.
 
I watched their video on tensioning the test media in the ATF-10G fixture. You just pull it till there is no slack in the test media and it is straight in the cutout for it, then tighten it down. The hardest part for me is holding the blade perfectly vertical and steady, then slowly pushing the edge down on the test media. My nerves aren't as good as they used to be.
I guess the test clips would be easier but I haven't used them much.
 
Interesting question. If I had to guess, I'd figure it would be what is done on razors for max keenness -- polishing on balsa strops embedded with successively finer diamonds. I use 0.5 micron/0.25/0.1 as my razor sequence after I come off my finest honing stone.
 
Diemaker said:
I just ordered a PT50A and will soon be trying to get the best possible score for a competition. I would rather learn from others than have to do all of the mistakes myself, and figure others here may be curious about this themselves. I have done a few searches that have come up empty so if I missed something let me know. I would like to keep this thread about how to do it and omit whether it makes a useful edge or not, which for me I am betting is a no. Still, I want to see how keen I can get a useful edge too.

I expect this is a toy I will get bored with in a few months so may do a pass-around with it if there is interest.
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I followed the original thread, which was pretty interesting. But it was difficult to come to any firm conclusions. Some found a highly refined and polished edge gave the best results. Others found a coarse edge made the cuts easier, perhaps because a point could get the cut started more easily.

If you have a knife to play with, I'd try it both ways -- coarse and polished -- to see what works for you.

You might also PM Jason B., Ankerson, Josh at REK or heavy hands. They did a lot of testing and came up with good scores. You could also call up the guy who invented it. His name was in Wootzblade's sharpness test thread.
 
The test media is 0.0095" thick as measured with my digital calipers. I would figure that the more acute angle would do better on the PT50A if the blade edges are sharpened to the same width at the apex. It seems like the more obtuse angle would push more against the test media, giving it a higher score. Anyway, that's how I picture it in my rookie brain.
I would like to hear what the experts say.
 
I think that blade sharpened without secondary bevel have more chance for better result .Free hand sharpening also have more chance for better score on test then sharpening on some guide tools ............ and skill and sharpening tools available , of course .
 
With the original BESS testing device I could have the test media break under its own weight with a carbon steel Japanese kitchen knife Sharpened to 4k and stropped with 1 micron diamond. A recurring trait was the test could be greatly skewed by adding a stropping step to the sharpening process.
 
The thinnest blade I tested performed the best, even though the edge prep was pretty suspect, stropped to hell and back. You're testing a pretty narrow performance criteria, thin is better and rougher edges need to have the across apex deviations cleaned up.

Many edges that would otherwise be considered sharp, long lasting utility edges won't score much under 40.
 
Jason B. said:
With the original BESS testing device I could have the test media break under its own weight with a carbon steel Japanese kitchen knife Sharpened to 4k and stropped with 1 micron diamond. A recurring trait was the test could be greatly skewed by adding a stropping step to the sharpening process.
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As I recall, the original BESS device had the 50g cup you filled with weights? So "zero" on the old one is equivalent to 50g on the current design. The original design couldn't measure anything keener than a cheap DE blade.
 
ToddS said:
As I recall, the original BESS device had the 50g cup you filled with weights? So "zero" on the old one is equivalent to 50g on the current design. The original design couldn't measure anything keener than a cheap DE blade.
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With absolutely nothing on the tester it would cut the line. No cup, no weight. The "platform" you set the cup on was all that was there and if that = 50 then the calibration would have been very off and none of the numbers would have been correct or correlate with the scale currently. If the testing method has changed and the amount of weight to cut the test media has changed then every test from the original BESS thread would be invalid.
 
Natlek said:
I think that blade sharpened without secondary bevel have more chance for better result .Free hand sharpening also have more chance for better score on test then sharpening on some guide tools ............ and skill and sharpening tools available , of course .
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I personally don't think that the sharpening system used would really matter much. WE, EP, KME, or by hand doesn't seem to me that it would matter. What seems to me that would matter is the width of the apex, and the angle of the edges. Also, polished edges would probably pass through the test media with less friction thereby giving a better score on the PT50A.
 
000Robert said:
I personally don't think that the sharpening system used would really matter much. WE, EP, KME, or by hand doesn't seem to me that it would matter. What seems to me that would matter is the width of the apex, and the angle of the edges. Also, polished edges would probably pass through the test media with less friction thereby giving a better score on the PT50A.
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I think the consistency and control of the angle might. My guided sharpener will sharpen below 1.7 degrees with the stone on the front of the table, so that won't be a limitation of my guided sharpener.
 
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Diemaker said:
I think the consistency and control of the angle might. My guided sharpener will sharpen below 1.7 degrees with the stone on the front of the table, so that won't be a limitation of my guided sharpener.
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Yeah, that could matter. I don't have to worry about that with my WE130. But I would have to add a spacer block under my vise and use my Low Angle Adapter to even get close to that angle.
 
Jason B. said:
With absolutely nothing on the tester it would cut the line. No cup, no weight. The "platform" you set the cup on was all that was there and if that = 50 then the calibration would have been very off and none of the numbers would have been correct or correlate with the scale currently. If the testing method has changed and the amount of weight to cut the test media has changed then every test from the original BESS thread would be invalid.
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As far as I can tell, the major difference between the prototype that was tested by people here and the production version is that 50g offset. A blade that scored 30 on the prototype would score 80 on the (current) production version. The prototype was incapable of measuring sub-50 gram blades for the reason you experienced.
 
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ToddS said:
As far as I can tell, the major difference between the prototype that was tested by people here and the production version is that 50g offset. A blade that scored 30 on the prototype would score 80 on the (current) production version. The prototype was incapable of measuring sub-50 gram blades for the reason you experienced.
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Did Edge on Up publish a revised chart calibrated to DE razor values or have they moved on to some other metric?

I haven't been keeping up with any of that since the beta test.
 
ToddS said:
As far as I can tell, the major difference between the prototype that was tested by people here and the production version is that 50g offset. A blade that scored 30 on the prototype would score 80 on the (current) production version. The prototype was incapable of measuring sub-50 gram blades for the reason you experienced.
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So the test might be a little more accurate, interesting. Although, if the test media is still the same then obtaining low numbers through high levels of polish is probably still the game. If a 4k edge was showing the limits of the original scale then I wonder where the limits of the new tester are?

Has the test media stayed the same?
 
The theory is that the force to initiate the cut is greater than the force to complete the cut, so the goal is to penetrate a few microns, or maybe tens of microns and then the fibre cleaves.

My recollection is that these guys worked with tools for cleaving optical fibres and the test media is something developed from that experience. The jig was developed as a way to utilize that test media.
 
Interesting, I used to make parts for a company that did fiber optic test equipment, including fiber cleavers holders. If memory serves the cleaver itself was a ceramic blade with a single 30 degree bevel. I do remember the finish on the apex was very important, it had to be polished. I don't remember if the cleaver was for just glass fiber or the plastic fiber too? The quality of the cleave was critical to the quality of testing the fiber.

Is the "test media" just plastic fiber optic fiber?
 
First, if you want to make meaningful measurements and not "cheat", you need to be aware of how to use the tester. Two things:

1. Just make the media "taut", not super tight. There should be zero tension in the line ideally. If you make it "tight" then it will pull apart under that tension after some depth of cut. This makes it read falsely sharp; AKA an overly low score that isn't real.

2. A pure push cut is what you are trying to do when you bring the blade down onto the test media. If you slice the cut by drawing the edge across the media you can get much lower scores than you should because you are not allowing the force of the cut to sever the media. So push, don't slice, otherwise you'll get falsely low readings.

In my experience the best scores are achieved by a more polished edge. All of my sub-100 edges have been polished to some degree or other. I haven't really tried for "lowest score possible"; I'm not all that interested. But I was initially quite proud when I made some mildly polished edges that scored 110 to 120. I think those edges were 600 or 400 grit (can't remember).

My videos showing toothy versus polished performance clearly show that the BESS tester shows lower readings on polished edges, even on very similar blades.

Good luck!

Brian.
 
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