Using kitchen scale

[SHARPCO]

Someone says, "You don't have to buy expensive BESS tester, you just need BESS media and a cheap kitchen scale." 

How can you dispute this opinion?

[Ken S]

Sharpco,

I would say that I accidentally did essential that. My PT-50 tester is the original model. The Sharp Check feature must be turned on manually. I did not remember that for quite a while. When I did a sharpness, I had to quickly try to guess the highest reading before the scale read zero. This made for very inconsistent wild guess measurements.

I was ready to return to using my KN-100. Fortunately Mike pointed out my error. I have been a happy camper since then.

Using a cheap postal scale instead of an Edge on Up tester is like trying to accurately torque engine bolts using an ordinary wrench instead of using a torque wrench.

Ken

[KnifeGrinders]

Someone says, "You don't have to buy expensive BESS tester, you just need BESS media and a cheap kitchen scale." 

How can you dispute this opinion?

He who says that didn't check what a quality scales cost. A cheap scale won't have the needed resolution. While a quality scale with resolution of 5 grams costs more than the PT50B, almost twice more; let alone the 1 gram resolution of PT50A.

Obviously, PT50 is more than a scale, it also has the platform over the scale for the fulcrum, and firmware with clever logic.

I've seen quite a few attempts to use common scales to test sharpness - the results are inconsistent to say the least;
I honestly think all these people are masochists - trying to make your own while having a BESS sharpness tester available is like re-inventing a bicycle but getting something hardly riding on its square wheels.

[Ken S]

Well stated, KG

Ken

[EOU]

"Someone says, "You don't have to buy expensive BESS tester, you just need BESS media and a cheap kitchen scale." 


How can you dispute this opinion?"

Thank you for the question Sharpco and your answers Ken and KG. In our opinion, using BESS test media and a cheap scale would be imminently more informational than cutting paper or shaving arm hair. Therefore, a step up. But then again, a washboard and a tub was a step up from beating your clothes on a flat rock next to the creek. The washboard and tub is not as efficient a laundering system as the modern washing machine but, we assume, would represent a smaller, initial, capital investment. 

We're all for cutting costs and do so at every opportunity around here but, in this case, it's simply not a practical solution. There are some things that have to be done correctly or you're just spinning your wheels. The PT50 Series is a system and not just  test media and a scale. That system includes high speed electronics, custom software and algorithms, specially designed mechanical measuring platforms and a means to accurately hold, dispense and accurately affix test media and all these things in a repeatable fashion. 

The PT50B updates the display every 100ms when the force applied is ascending in value, the PT50A every 40ms. The average, inexpensive, kitchen scale does so every 1.5 seconds. That's 15 times slower than the PT50B. Speed is critical to accurate measurements in that we want to capture, as closely as possible, the actual moment of severing. If one were to use a very expensive laboratory scale, one that acquired information as fast as the PT50B, there would still be problems remaining. The human eye integrates image information over a 200ms period of time. If data were coming in at a rate faster than 200ms (millisecond) you might never actually even see a good portion of it. That's why the PT50 Series captures and holds the final result, so that that your eye can integrate and fully interpret it. 

Here's something that you might find interesting and illustrates this whole optical integration thing. Take two different pulses of light, A and B. Both are of the same, exact, intensity (brightness) but A's pulse duration is 200ms  and B's is 100ms. Your eye will detect both of these very simple images but your brain will tell you that B appears to be only half as bright as A. If the pulse duration of B is then extended to 400ms while A remains at 200ms your brain will tell you that both are of equal intensity. They've both been fully integrated. More complicated images of short duration (like rapidly flashing numbers) are a little different. They may be interpreted as just blurs. 

The best instruction though is to look at Ken's answer. Even with the other benefits provided by the PT50B system present, he didn't experience very satisfying results until he pressed his SHARP CHECK key. We've even addressed that issue though; you don't have to press the SHARP CHECK key any longer, the new PT50Bs come up in SHARP CHECK mode automatically.

[KnifeGrinders]

An exhaustive explanation by EOU - also explains the specifications Acquisition Rate of 25 measurements per sec for PT50a vs 10 for PT50b, and the better precision of the PT50a.

BTW shouldn't Specifications be added as the last page in your PT50_Series_Manual_A_B_C.pdf ?

[Ken S]

There is a logical very low cost option. The problem with the paper cutting option is the variety of papers used. In itself, it is not a bad method. Spending around $5 US for a box of quality 20lb copy paper goes a long way toward making the tests consistent. With care and practice, one can soon develop a feel and an ear for good cutting.

Admittedly, this method has its limitations. It provides no repeatable numeric of sharpness like BESS. However, for the more casual sharpener or those on a tight budget, a well regulated paper testing routine has possibilities.

I have been corresponding with another bessex member who just purchased a PT-50A, the top of the line. He chose wisely. He is a machinist, accostumed to working within very tight tolerances. Regardless of his actual sharpness needs, he would not feel comfortable working with a tester which did not have the highest accuracy.

I was quite content with my KN-100, and am very happy with my original PT-50. However, in hindsight, if it had been available at the time, I should have purchased a PT-50A. I had no idea then how involved with sharpening I would become.

Ken

[EOU]

Good suggestion KG. The specifications for all electronic units can be found on our website under, auspiciously enough, "Specifications" linked next to each instrument . It would be a simple matter to append them to our operating manuals and will put that on our to-do list. 

Some information is better than no information Ken and cutting paper must provide information. There must be paper and then there is paper though. Customers report that 150 edges cut paper and customers report that 500 edges cut paper. Perhaps they are cutting different sorts of paper and in different ways. We're not very good at cutting paper around here and equating the perceived result to a BESS score so our opinions on the matter are colored by our lack of success. It seems to us that we have better success cutting paper with a knife sharpened to 150 than a DE razor blade at 50. Could be tooth versus polish in this case or it could be we just don't know how to effectively cut paper. Seems like that's a skill set that we should have picked up back in elementary school. Oh the travails of a misspent youth.

[grepper]

I would rather have a PT50A than my PT50B even though I really don’t need a PT50A.  I would rather have a PT50B than a PT50C.  I would rather have a PT50C than use paper.  I would rather standardize on a particular type of paper rather than a different type of paper each time.  I would rather cut paper than use my tongue to test edge sharpness.


Jump to into the video to 8:45:

https://www.youtube.com/watch?v=MvLuDRsEMCY

[EOU]

Via the Socratic method Grepper, that is the best argument for purchasing an electronic edge tester that we have ever seen put forth. Buy an edge tester or cut your tongue, the choice is yours.