Using a Sharpening Steel
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I just had the pleasure of spending the afternoon with Mingjia Liu, principal oboist of the San Francisco Opera (http://sfopera.com/about…/people/bios/orchestra/mingjia-liu/). He uses the Wicked Edge to sharpen his reed knives, which is a big part of the skill set needed for playing the oboe because each musician creates their own reeds. Mingjia has a very good video on the process here: https://www.youtube.com/watch?v=zbdFPepEHL0. Part of his sharpening technique is to use a steel after sharpening to establish a burr that cants to one side. Reed musicians like have the burr as in aid in scraping very minute amounts of material from the reed as they’re shaping it. We worked on some knives together while he was here and later I took a look at the edges under the scope. What I found was pretty interesting – the micro-bevel/burr that was formed with the steel comes at the expense of a certain amount of steel. There is a noticeable fracture line between the original apex and the bit of metal that is pulled up into the wire edge. In this case, it was about 30µ. What that means is that the knife will lose about 30µ (0.03mm) of metal every tme it’s sharpened. Check out the image here:
You can see the scratch pattern from the 3µ lapping films going in one direction and then the scratches of the micro-bevel/burr going the other direction and the fracture lines along the shoulder. Those fractures were present throughout the entire length of the blade I examined.
It may be that the burr is so essential in reed carving that the metal has to be sacrificial but it makes me wonder about using a steel on a good kitchen knife and if the potential metal loss is a concern. It would be easy enough to measure with a micrometer, you wouldn’t even need a microscope. You would just measure the width of the blade before and after steeling for a number of times and track the loss of metal. If anyone wants to study it and report back, that would be awesome.
-Clay
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Tom, here are some images at various magnifications that I took of the ThermoMorph impression I made of the knife blade:
You can see in the lower magnification images that the blade face is parallel from the spine to where the grind begins, and then it’s hollow ground to the bevel. It’s asymmetrically ground overall, leaning to left when mounted in the Wicked Edge. This slight bias is for right handed users and creates a sort of scooping action when the blade is drawn across the reed. Incidentally, the knife is held roughly perpendicular to the reed both in terms of the face of the blade and the spine of the blade so that the knife is nearly vertical and forms a cross with the reed. Although Mingjia sets the sharpener at 24°/22°, the actual included angle is closer to 15°. This is because he’s built a special holder for his blades that sits up much higher than the regular position and clamps the knife by the handle, a little like the Tormek adapter.
-Clay
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