Steel

Is Rockstead The Sharpest Knife Ever?

A Real Rockstead.

Would you be happy to spend two grand for a folding knife? If you are, you’re probably either a Premier League footballer or a Russian oil tycoon, and you probably already know about Rockstead knives.  If not, make the jump to read more…

The TEI-S DLC in this video is made from Hitachi YXR-7 high speed tool steel that’s hardened to 65.7 HRc. You read that correctly: sixty-five point seven. And that stippling on the grips? Genuine stingray skin, just like you’d find on a traditional katana.

Of course, two grand could also buy you a pretty nice katana, if that’s what floats your boat.

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Discussion

13 responses to ‘Is Rockstead The Sharpest Knife Ever?

  1. Rockwell hardness isn’t everything. A knife that hard is extremely difficult to sharpen, and is usually brittle, too. Your knife won’t help you if you drop it and the blade shatters like glass.

  2. I bought a Kershaw Crown folding knife today for $15 at Walmart. I know how much more money the Rockstead costs. I’d like to know how much better, to make the monetary difference worth it, the Rockstead will cut than the Kershaw Crown.

  3. This is what happens when engineers get a budget to solve common problems. You end up with exquisite solutions.

    First, to their steel: The steel they’re using is more commonly used in molds, punches and dies for forming steel parts – hot or cold. These mold/die steels need to be hard (so they don’t wear when working softer steels), but “tough” (resistance to impact breakage) so that the punches and dies don’t crack out after repeated impacts.

    Here’s the phase diagram for this class of steels (“Matrix high speed steel”) vs. a much more conventional HSS, M2 (I use M2 in machining toolbits all the time – it’s a cheap, ubiquitous tool steel for lathe and milling cutters):

    http://www.matrixhighspeedsteels.com/3_34_concept.htm

    That’s pretty impressive. They’re achieving this by controlling the size of the carbide grains in the steel and keeping them small and uniform – also impressive.

    But there’s a downside to these steels: Sharpening them becomes a challenge for most people. You need to be using ceramic or diamond abrasives, and the shape of the cutting edge will be difficult for the average knife owner to maintain. Here’s a pic sequence of Rockstead’s method of maintaining their edge:

    http://rockstead.jp/maintenance/

    The lapping is old news to me. That paper holder they have has just given me an idea on how to make one for use in the gunsmithing shop. There’s some amazing new abrasive papers available today, and a good paper holder on a surface ground piece of steel would make working on things like triggers much easier.

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