A Comparison of Several Manufactured Blades

Gillette_blue_blade_x_04
Vintage NOS Gillette blue blade (E3, manufactured third quarter of 1959)
Gillette_blue_blade_x_02
Vintage NOS Gillette blue blade (E3, manufactured third quarter of 1959)
Kai_scalpel_x_01
Kai/Miltex disposable scalpel blade
Kai_scalpel_x_03
Kai/Miltex disposable scalpel blade
Astra_stainless_X_05
Modern Gillette Astra Stainless DE razor blade
Astra_stainless_X_01
Modern Gillette Astra Stainless DE razor blade
olfa_blade_x_03
OLFA disposable snap-blade knife
olfa_blade_x_01
OLFA disposable snap-blade knife

All four examples have a cutting edge with a width less than 200nm, although the final bevel angle varies from 21 degrees for the Blue Blade to more than 40 degrees for the Olfa blade.   The Olfa blade also has a small burr on the edge which reduces the effective keenness.

olfa_blade_x_05
Edge Burr (foil or wire) on the Olfa snap blade.

At minimum, these examples demonstrate the scale at which we need to resolve and image features is well under one micron.

With our definitions of Keen and Sharp we can see that all blades have similar keenness, but the razor blades are sharper than the scalpel and utility blades.  The images below demonstrate that the Feather Super Pro Artist Club blade is much keener than other manufactured blades, but is not nearly as sharp as a conventional straight razor.

Feather_AC_SP_01
Cross-section of a Feather Super Pro Artist Club blade, often considered to be the “sharpest” commercial razor blade. The blade is coated with a fluoropolymer that is removed with the first use. The Apex width is approximately 50nm, keener than any of the commercial blades shown above. The width at 3 microns is 1.4 microns, due to the 19 degree final bevel angle.
Shap16k_X
Cross-section measurements of a conventional straight razor, honed to a 16k whetstone, prior to stropping. The edge width is on the order of 100nm, less keen than the Feather Super Pro; however, the width at 3 microns is only 1.05 microns, significantly Sharper than the Feather blade.

  11 comments for “A Comparison of Several Manufactured Blades

  1. Seraphim
    May 5, 2016 at 3:57 pm

    I believe your Feather edge measurement data is in error.

    You are not measuring the actual final edge bevel.

    Please see my post here:
    http://badgerandblade.com/vb/showthread.php/489421-New-gd-207-with-goldwash?p=8214165#post8214165

    Like

    • May 5, 2016 at 4:07 pm

      You have opened a large can of worms, my friend. The “actual final edge bevel angle” is ALWAYS 180 degrees.

      Through experimentation, I have found that taking the angle between the tangents at about 3 microns from the apex is an excellent measure of the degree of micro-convexity introduced by stropping.

      You may wish to read this thread (brush up on your Calculus first)

      http://www.bladeforums.com/forums/showthread.php/1284628-Ideal-and-Real-Geometry-of-Convex-Edges

      The Feather Super Pro has a 10 degree bevel with a 19 degree microbevel (these measurements are plus or minus 1 degree).
      Feather_super_pro_06Feather_super_pro_03

      Like

  2. eKretz
    May 11, 2016 at 4:26 pm

    It does appear that the last micron or so is at a steeper angle than 19° – and it doesn’t look like convexing but a separate tiny bevel. How they are putting that last little bit on the very edge would be interesting to know.

    Like

    • May 11, 2016 at 5:42 pm

      It is not possible to micro-bevel at this scale – this is standard micro-convexity produced by stropping. The uniformity of the apex is also indicative of stropping.

      Like

  3. eKretz
    May 11, 2016 at 8:44 pm

    Ah, must be the scale I’m not used to. At that level it sure looks like a tiny microbevel! These blades are likely finished in strip form, right? So they must be doing a power stropping or brushing of some sort. Sure would be interesting to see the factory floor and have access to the processes used.

    Like

  4. August 4, 2016 at 10:26 pm

    I was in Japan, so I got my wife to purchase me a case of Feather Super Pro blades off of amazon.jp. I had my first shave with them last night, and it was a great experience. Feels similar to a straight razor using your progression, right after refreshing.

    Like

  5. Jason D. Stone
    January 16, 2017 at 4:31 pm

    Great work Todd! I have found that on some brands of these blades, they need to be stropped or micro-beveled to get them to cutting well, and it can vary from blade to blade even within brands. Take care!

    Like

  6. Stefan
    July 3, 2018 at 4:13 pm

    Love this post, thanks!
    Too see the plastic coating in the section makes me wonder how the blade can cut hair.
    Perhaps the plastic was deformed.
    In the picture with section cut the blade width 3 micron from the apex is doubled with the plastic.
    And the apex itself is totally covered in plastic.
    How can the blade penetrate and cut hair with this coating?

    Like

    • July 6, 2018 at 9:03 am

      The thick layer of teflon/polymer is removed with the first use, leaving just a nano-scale thin layer on the steel.

      Like

  7. IdanP
    July 23, 2019 at 4:14 pm

    Hi, can I ask how exactly is the cross section image constructed?
    I am a little confused by it; does the program simply shift part of the edge downwards or is there an actual physical “cross section” (i.e. cutting the edge across) going on?
    Regards.

    Like

    • July 29, 2019 at 12:25 pm

      The edge is cut and polished with a focused ion beam to show the cross-section geometry.

      Liked by 1 person

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