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Razor Blade Sharpness Chart

Discussion in 'DE Blades' started by Bogeyman, Saturday November 11, 2017.

  1. Obelix

    Obelix

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    In science, a theory to be accepted as true and not just a wacko theory, must 1) be able to the explain every situation , 2) must be accepted and reproduced by others.

    In his measurements, there are non PTFE blades (even simple stainless) that according to him, get sharper as shaves progress. Assuming that the urban legend that human hair is tougher than copper filaments of the same caliber is true, as well as empirical experience that a blade usually withers with shaves instead of becoming sharper, the theory that could work for Derby, doesn't work for the rest. Even platinum coated blades, should not become sharper with use, since the platinum is put there are hardening agent, to prevent the edge of getting damaged early on.

    At any rate, let us assume that i am wrong. Let us assume that this one is also wrong:
    https://mielabs.coe.neu.edu/sites/mielabs.coe.neu.edu/files/Razor Blade Sharpness Testing.pdf

    (Because, they can't BOTH be right, can they...).

    I find it amazing, that people pay for that expensive machinery instead of such a simple method and that in engineering faculties, nobody has thought of it and even worse, teaches different things!

    https://www.researchgate.net/publication/280821670_MEASURING_CUTTING_FORCES_IN_MACHINING_PROCESSES



    [​IMG]

    Or, instead of making students sleep, "grab a scale".

    But, dem scientists, they want to overcomplicate things...
     
  2. Obelix

    Obelix

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    Double post, sorry, internet problems.
     
  3. invicta

    invicta

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    Indeed there are some results that are strange and I was not seeking to defend the results. The stainless steel blades like Astra SS do seem to get sharper and only the manufacturer knows what is on the edges that impedes the initial sharpness but then gets worn away in use. That improvement in sharpness is short lived and degradation of the edges continues with use as would be expected. The testing only goes as far as 2 head shaves so is limited in it's results.
    The human hair can be as strong as copper wire of similar diameter in terms of tensile strength. It is the tensile strength that is often taken out of context because it has nothing to do with resistance to cutting by a sharp steel edge.
    What the test results don't explain is smoothness. People have varying views on this parameter of a blade so that remains a mystery. Preparation, skin type, effects of UV on the skin all lead to a variation in blade performance.
    I could not get to the mielab site which in not secure.
     
  4. Obelix

    Obelix

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    Look, i am not a physicist, so i don't claim to be a scientific voice in this. However, until someone provides a document, video or anything from a scientific source, when using a scale is recognized as scientific method of measuring blade sharpness (or cutting force to make it more broad and easier to provide such proof), i stick with regarding "weirdness" as charlatanism. I mean, SURELY, someone else must have at least mentioned this somewhere in a paper in the depths of the internet, other than a shaver's blog!

    I would also be very curious to hear, why his readings are right and the other guy's here

    https://mielabs.coe.neu.edu/sites/mielabs.coe.neu.edu/files/Razor Blade Sharpness Testing.pdf

    Are wrong. Because, the cases i see are:

    1) They are both right. But their results are different, so there's a problem with this case.
    2) One of the 2 is right, the other is wrong. Plausible, but i couldn't explain why.
    3) None of the 2 are right. Plausible and a probable explanation is that none uses a scientifically approved method.
     
  5. Boru62

    Boru62

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    The Perma-Sharp surprised me and also clarified something.
    The first shave was in a Star DE and I've had much better shaves with this razor.
    The second shave was in a Slim set on 7 and it was a great shave. I put it down to the razor but it was also because the blade was significantly sharper on the second shave.
     
  6. Obelix

    Obelix

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    The other guy's results are these:



    [​IMG]

    It's from a guy in Badger and Blade apparently.
     
  7. Bogeyman

    Bogeyman

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    He doesn't know what blades are coated with PTFE and neither do we. You are assuming that. Names such as "Platinum" & "Chromium" are meaningless and are more often than not merely sales pitches. All modern stainless blades have some coating lest they shave like the Treet "Black Beauty" that he tested. The coatings aid in smoothness obviously, but the sputtering and substrate metal/alloys are what holds the edge. That is where the rubber meets the road.
     
  8. Obelix

    Obelix

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    Where the rubber meets the road for me, is one, single scientific source, that proves that his method can be used for accurate cutting force measuring. The rest, is pure speculation. Because also the other guy claims to measure the same thing and finds different things and others yet, write scientific papers and forget to mention "you can use a simple sensor such as a common scale".

    Last post from me, because there is no point in trying to add anything else that i haven't said already.
     
  9. Here's another chart. This guy Squire uses a high powered microscope to examine blade grind. His top two blades seem to be the Gillette 7 O'clock Sharp Edge Yellow @ 7.5 and the Derby Extra @ 7.0.
    http://forum.shavemyface.com/viewtopic.php?t=29705
     
    Obelix likes this.
  10. SeanC

    SeanC

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    Although variables such as razor and soap can be controlled, I struggle to see how any kind of 'face feel test' can be valid beyond the tester himself as we all have different skin, techniques and facial hair.

    Sent from my LG-H815 using Tapatalk
     
  11. Interesting but a bit pointless really.
    I like knives and other sharp things and mostly I sharpen my own; axe, machete, penknife, cook's knife, paring knife whatever they are all different. Without knowing the relative hardness of the edges and the angle of the edge and how that relates to the angle of use, nevermind what treatments have been applied what does that test show?
     
    Bogeyman and Blademonkey like this.
  12. Well it made for a lively debate if nothing else :) P.
     
  13. That pretty much sums up my feeling, no amount of testing in the world is going to shake my (admittedly contrarian) view that Feathers are crap.
     
  14. Right with you there!
     
    Blademonkey and chris.hale like this.
  15. Bogeyman

    Bogeyman

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    After you pony up the cash for this machine I will gladly supply you with that your heart desires:

    http://www.catra.org/pages/products/kniveslevel1/st.htm

    :D ;)
     
  16. pimple8

    pimple8

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    This testing confirms a lot of my conlcusions and some "common truths" out there i.e. Feather is very very sharp and drastically looses sharpnes after each shave, Rockwell razors blades are the dullest and so on.


    Sent from my LG-D855 using Tapatalk
     
  17. Which will result in the same sort of data set so ...why?
    I had to teach my daughter how to use a knife to carve wood and not blunt her knife in minutes i.e. cut at an angle not perpendicular to the surface - or use a blade with a less acute edge.
     
    Bogeyman likes this.
  18. Bogeyman

    Bogeyman

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    If you read all of his blade reviews things (at least for me) fall perfectly into place per my experiences. The Feather is the sharpest initially at his score of 32 (lower being sharper) and the closest is the Nacet Stainless at 39 which for the latter makes sense as it's marketed in the Middle East where men are more hirsute on the whole. The real surprise for me is the Bic Chromium Platinum which starts at 40 & then drops to 33 after the first shave and then 32 after two shaves. This however makes perfect sense as many say (including myself) it shaves rough after the first shave which is because it's getting sharper as the coating quickly wears away sooner than almost all other blades it appears. The price to pay for initially being too sharp (or a poorer coating?) for the Feather is a rapid "death".

    The takeaway is that the blades that most gravitate to are the ones that are consistent and are a veritable balancing act between sharpness & smoothness with no small part due to the longevity of coating as it wears down. There is pure genius in the simplicity of his rating system that just flat out makes sense to this reader.
     
    Fergiebilly and SeanC like this.
  19. [​IMG]
    I Can Have these Blades Anywhere I Want them as I Hone My Own..These Don't Dull Like Factory Blades as they Get Maintained Between Shaves..No MAGIC COATING..Just Pure Swedish Carbon Steel..The Best..I Will Never Put a Factory Blade Near My Coupon Again..;)

    Factory Blades are Barbaric Compared to these Full Hollow Grinds..:D:D

    Billy
     
    Last edited: Tuesday November 14, 2017
    Bogeyman, Benz3ne and William Dobson like this.
  20. I think you are on the right track. When I used to make wooden furniture all my chisels and hand plane blades were made out of high-carbon steel. I sharpened them on a thick piece of float glass and used 3 to 4 grades of metal type sand paper: starting with a low number grade and ending up with 1200 grade. High-carbon steel can be made very sharp but is pretty brittle. I have never seen good hand tools made of stainless steel and every artisan I knew always hand sharpened their tools. Some used sharpening stones with oil and others used the float glass/sand paper method.
     
    Last edited: Tuesday November 14, 2017
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