Grinding the Ura and Why

So you want to make some Japanese cutting tools, kanna, whatever, and you get past the hurdle of forge laminating tool steel to something softer. Then comes flattening the back and there is a wide ocean of very hard steel to waste away your expensive sharpening stones. How about hollowing out the back (Ura) and greatly easing all of the subsequent work?

The old school approach would be using sen on the annealed blade prior to hardening, but a quick look at most of my own tools from japan show a ground finish. Sen, well, are nice, but it takes the time and charcoal to make them and even full process annealed tool steel is hard stuff compared to the buttery/gummy consistency of lower carbon steel. Sen are also near impossible to use without a rock solid sen-dai.

Apparently I’m writing a blog post about something almost no one on the internet cares about. If I was writing about katana it would be a different story, plenty of interest there. Certainly there are many talented modern swordsmiths outside of Japan who could do a good job making tools, you know, stuff not made for killing people. Why don’t they give it a try (nudge, nudge). If you care to search for methods of hollowing ura dear Jason Thomas pops up, but he’s to busy swinging in his hammock daydreaming in Hawaii to help us poor uneducated blokes out. Just kidding, I’m sure he’s hard to work at something, which we all would like to know!

Back more to the point, how does one hollow the ura without a lot of fuss? I use the edge of my 8″ grinding wheel, which is just about perfect for backs 1/2″-1″. You can even make a little jig consisting of a board with a fence hinged at one end to keep the grind radius centered on the tool.

Take as an example this little kanna blade for a dovetail plane I made from some 0-1 steel forge laminated to mild steel. You get it all dimensioned and pretty in the annealed state and then quench it and it warps. So you temper and some of the warp comes out, then you can hammer straighten it at the anvil to the best of your ability, hopefully without cracking the tool steel. If you already had the ura shaped it wouldn’t be even by the time the back was flattened on a bench stone. And everyone wants that nice aesthetically pleasing ura.

Grinding the ura after tempering saves a ton of work. If you’re making narrow tools you’ll want a stone smaller in radius than 8″, if you’re forging kanna you’ll find yourself lusting after the really large Japanese water cooled grinding stones.  Some ura are elliptical, some a more true radius, let your eye be the judge of the progress.

I’m trying to save wear on my sharpening stones, they wear down fast with work like this. In the above photo the back was still low at the cutting edge, so I took the blade back to the grinding wheel several times and ground the ura back completely to the outside edges of the blade.

Here’s the finished ura, done freehand. Its not perfect, but you wont hear me complain.  The grinding gets shallower towards the cutting edge, the shape produced naturally by the radius of the grinding wheel, easy right?

Two blades, my best forging work by far, ready for a dovetail kanna dai to be made.

The bevel on the kanna looks weird because it tapers across its width. A dovetail kanna is a side escapement plane, there being no wedge, it is held into the body by said wedging shape. The knicker iron is also a tapered sliding dovetail. I quenched the knicker iron a bit too hot and its coarse grained, you can feel it when sharpening. The blade though, maybe good enough for me to sign.

I need to get my hands on some wrought iron.

9 thoughts on “Grinding the Ura and Why”

  1. nice post Gabe. I’m currently using the edge of the grinder to make y uras, mostly on old chisels that need some love. Haven’t made a guide for it tho, yours are much more consistent. To grind a kanna one could use the same setup but with the guide put at an angle instead of horizontal, this would increase the apparent radius of the grinding wheel. I’ve done this also with an angle grinder, where it’s easier to change the angle between wheel and blade. Lovely blades btw, look really professional.

  2. Gabe, I found that I needed to go back and forth between flattening and grinding of the hollow to get nice even legs. It was a large amount of work!

    Given how difficult this is it always amazes me to see a black-back that turns an ito-ura.

    Very cool work!

    PS You might want to contact Jim Blauvelt, he’s been making Kanna and using a sen to scrape the hollows.

  3. “Apparently I’m writing a blog post about something almost no one on the internet cares about. ”

    Oh, I wouldn’t assume that. I have dug hard for information on sen a bunch of times, and I’m sure I’m not the only one. I suspect there are plenty of interested folks…
    I’m confused on two things though. One, I thought sen were for scraping (and tapering) saw plates. I had not heard of them being used for ura. Two, I have never heard of a sen dai; in the (very few) pictures I’ve seen of sen, they have big handles, almost like a drawknife has. Anything you can add to enlighten me?

    Nice post Gabe, keep up the good fight.

  4. I want to ask that as you develop your technique for grinding an ura, you make a video or simply go into more detail as to how you set up your grinder and mount the chisel for moving it across the grindstone.

    1. I think this will deserve another post, especially after the mention of Jim Blauvelt. I heard from Yann that Jim won the planing competition for north east usa kezurokai in 2015 with a kanna he forged, the guy obviously knows what he’s doing. Last I looked he had very little info online other than the odd youtube video of him giving a class. I have some videos from the Takenaka carpentry museum of blacksmiths grinding and honing ura for kanna a couple different ways, I’ll put those up soon.

    2. “I want to ask that as you develop your technique for grinding an ura,”

      Hand techniques are always best, but you could easily clamp a piece of flat stock to the end of the blade that went off at 3 o’clock and was held in a slot, so the blade would be presented right from the side of the wheel, you could have a vertical stop to center it. That along with the right wheel diameter would be pretty much chimp proof, and require very little in the way of permanent fixturing unless you wanted to set up for it.

  5. Ha! I laughed so hard, I nearly fell out of my hammock, and consequently put my Mai Tai at great risk! And….you are completely correct in that I should start posting again. I could definitely use the incentive to kick up my work a notch, my style points currently being a big fat zero at the moment, haha.

    You, on the other hand, are doing some great work my friend. Very clean! Your design notebook alone turns me green with envy.

  6. I don’t really buy the idea that grinding an ura saves a lot of work. If you have power tools, then you can grind flat, no problem, to make an ura you have to dish it out, which is one thing, make it look good. Then the poor schmuck on his knees get to grind all that hard steel out again as he works the bevel back. Most Western guys never get much wear on their tools either because they don’t do much, or because they are constantly making or buying new stuff. But a real carpenter will use up a lot of tools and polishing out the ura over years is a lot more work than dealing with a flat back.

    I don’t know how much sense it makes to say it is for preserving stones (though you like me may be adverse to wearing ours). The SC grit and kanaban method work great, just a lot of work.

    The only explanation that makes sense is that the ura is there to even out the effort required to sharpen tools. In the west for a while anyway, and during the period I cam up, they taught only sharpening the bevel, you didn’t polish the back, except to get off the wire edge. Of cours there are almost as many methods as there are makers, but that was pretty common in the books from the revival period of the 70s to the 80s. Not a good method. Not what we do with knives, or how the Japanese sharpen equally finishing both sides of the edge. That is what the URA does, makes the number of strokes per side come out evenly. This is also makes sense with the observation that a blade with a nearly worn away ura is at it’s best.

    For tool making a belt sander is crazy fabulous. the 2×72, 1×42, and 1×36 all have good grades of belts available for them. One thing you can do with the flat platen is put a curved piece of wood under it that gives you any radius you want, you can have a 60 foot wheel. Wood is ok for a little grinding, if you want uninterrupted heavy grinding, you may need to source some of the graphite paper, or whatever they sell these days.

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