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5 BESS? Is it possible?
#1




Check 8m30s
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#2
Thanks for pointing to the video, SHARPCO
What a bubbly pair! I like their "child safe" definition for the sharpness over 600 BESS.

Mike will probably correct me, but I believe one needs a PT50A to discriminate in the under 50 BESS range, and even so any score under 10 is just that, "under 10" because of noise and unavoidable measurement errors.
The PT50B updates the display every 100ms, while the PT50A every 40ms.
With the PT50B that these guys use, the edge must be pressed against the test media line for at least 0.1 second to get an accurate value - in the video it is less than that.
http://knifeGrinders.com.au
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#3
Really? Holy crap, that's sharp!

I would be very interested to see how it would perform in a SET test.
I wonder what the sharpness would be after sitting overnight. Ooops. Correction. He said he sharpened it a few days ago. What's up with that?

I was not aware that it was possible to sharpen a blade to 5.

Holy crap, that's sharp!
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#4
Well we guess that settles the debate concerning whether a straight edge can be sharpened to the level of a DE razor blade. In explanation of how the PT50B with 5 grams of resolution calculates BESS numbers it goes like this; anything calculated at/including 7.4 grams down to 2.5 grams will be displayed as 5 grams. Anything above/including 7.5 grams up to/including 12.4 grams will be displayed as 10 grams.  In theory, the impossible, a reading of "0", would be possible with a PT50B and to a much lesser extent a PT50A due to this rounding function. In fact, a PT50C with 25 grams of resolution might have given these YouTubers a reading of "0" with their straight edge razor. Having offered up this explanation, it is misleading because, in reality, all values that fall outside (or inside however you choose to look at it) the resolution of the instrument are just noise.

In any event, these guys did offer up a very entertaining demonstration of the capabilities of a PT50B. We do wish that they would take better advantage of the knife fulcrum but, in fact, when working with edges that are very sharp (under 150)  use of the knife fulcrum becomes less critical. Thanks to SHARPCO for bringing this to the Exchange.
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#5
(08-20-2018, 10:05 AM)EOU Wrote: Well we guess that settles the debate concerning whether a straight edge can be sharpened to the level of a DE razor blade. In explanation of how the PT50B with 5 grams of resolution calculates BESS numbers it goes like this; anything calculated at/including 7.4 grams down to 2.5 grams will be displayed as 5 grams. Anything above/including 7.5 grams up to/including 12.4 grams will be displayed as 10 grams.  In theory, the impossible, a reading of "0", would be possible with a PT50B and to a much lesser extent a PT50A due to this rounding function. In fact, a PT50C with 25 grams of resolution might have given these YouTubers a reading of "0" with their straight edge razor. Having offered up this explanation, it is misleading because, in reality, all values that fall outside (or inside however you choose to look at it) the resolution of the instrument are just noise.

In any event, these guys did offer up a very entertaining demonstration of the capabilities of a PT50B. We do wish that they would take better advantage of the knife fulcrum but, in fact, when working with edges that are very sharp (under 150)  use of the knife fulcrum becomes less critical. Thanks to SHARPCO for bringing this to the Exchange.

In my experience using the PT50A tester freehand, I found that you have to be really careful not to move the blade horizontally or contact the media with the knife at an angle.  Instead of true push cutting I add a slicing component to the test.

I have to be super slow contacting the media, with the edge even on the horizontal plane, or my readings are misleadingly lower.

Like EOU, I would have liked to see the fulcrum used.

Ed K.
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#6
Very interesting topic and video. 

Mike's comment about the sensitivity range of the PT50-B says a lot about his knowledge of his products and, just as important, his integrity. Mike is acknowledging a fact of precision measurement; every measurement tool is designed for a particular range of accuracy. Numbers are only meaningful when the user knows the context.

For those who want to learn more about measurement and who are not afraid of a readable book of many pages, Inspection and Gaging is a fascinating read. It was first written to bring new factory recruits up to speed during WWII. I enjoyed reading it and have found its information valuable. Here is a link:

 https://www.amazon.com/Inspection-Gaging...and+gaging

My everyday tester is the original PT-50. Its accuracy range more than meets my needs. If it had been available at the time, I would have purchased the top of the line PT-50A. The EOU line up of testers follows industry practice of having tools for the worker on the factory floor; inspection tools for product inspection and periodic checking of the floor tools; and laboratory tools for the most critical work. For the home cook, the PT-50C is the perfect tool. It is compact, easy to use, relatively inexpensive, and has more than enough accuracy. The PT-50B is the ideal tool for the sharpener. It delivers noticeably higher precision than the C version at reasonable cost. When we get into discussing the "KnifeGrinders" range, we are in the domain of the PT-50A range. I do not feel that I need the PT-50A to participate in the discussion, however, if I was regularly posting with high accuracy BESS readings, I would upgrade.

I found the video quite interesting, however, working that way would soon bankrupt a farmers market sharpener. I am fascinated with pushing back the sharpness frontier, however, I am more of a Grepper sharpener. I want very sharp edges consistently produced in a time efficient manner. My kitchen knives just need to work.

Good topic; thanks for posting it.

Ken

ps I like the 600 BESS "child safe" designation.
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#7
Thank you Ken. Your provided  link and article is very appropriate to this discussion. Thank you to ED  for pointing out something important to the measurement process that we didn't. The knife fulcrum does steady the edge and guards against any sort of "slicing" movement over the test media. We use the knife fulcrum each and every time we take a measurement with these two exceptions; when it is impossible or impractical to do so. You can't use the fulcrum when measuring a DE razor blade and you can't use it when measuring many industrial and woodworking edges but when measuring knives and other edges of similar form we say, use it!

There are now a dozen or so YouTube channel folks who have integrated our instruments into their video reviews and demonstrations and we have learned a great deal by watching these videos. Believe it or not, people don't always take time to read the instruction manual. Isn't it interesting how sometimes you have to get hit squarely between the eyes with something you already knew before you really see it? For that reason we have now printed up a "Quick Start" guide that is now part of every electronic tester package. Quick Start guides have been included with our analog line of testers since their initial offering. While all BESS Exchange members are meticulous in their approach to edge testing there may be some newcomers who stumble across this thread who may find benefit in our new Quick Start guide so here goes: 

                                                         
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#8
I facebook group I have set up has a few members with both testing bases with the Jig you have consistently scoring lower than the 45deg Jig, If I replicate the extra line tension from the old jig, I can score 5 on my razor too Smile- if I leave a bit of slack it scores 50... I dont see how a smooth shaving razor can score that to be honest, hair severs on contact.
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