Stones That Redefine Sharpness

Jim Morgans Wood Profits

Jim Morgan's Wood Profits

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Editor's Note: In the past year or so almost every woodworking catalog in the U.S. has started to carry Japanese tools — especially Japanese water stones. It's hard to recall such quick acceptance of any other "new" tool. But is all this excitement justified, or is it just another gimmick?

About six months ago we decided to get some Japanese water stones and try them out in the shop. To make a long story short, we like them — a lot. But we did encounter one problem. There's very little information about these stones.

That's when we contacted Fred Damsen of Woodline, The Japan Woodworker to find out a little more about these stones and how to use them.

Woodsmith: To start, I'd like to get some background information on Japanese water stones. Can you tell me a little about them?

Woodline: Well, first of all, there are two different types of water stones; naturally mined stones and man-made stones.

The natural stones have been mined in Japan for about 2000 years. But approximately 1200 years ago the best deposits were discovered in the Narutaki district (a mountainous area north of



Kyoto). The natural stones were originally used to sharpen tools, knives, and that sort of thing. But the real development of the natural stones occurred as a result of the Japanese preoccupation with swords and armaments.

Woodsmith: When did the man-made stones come into the picture? Woodline: I don't know an exact date, but it's been in the last 80 years or so. . . after the turn of the century. Woodsmith: I didn't realize they are such a recent development?

Woodline: Yes. The man-made water stones came about because of a scarcity of good quality natural stones . . . which forced the price up.

Woodsmith: I've noticed in your catalog that natural stones (Awase Toishi) are priced in the range of $25 to $400, so let's get back to the man-made stones which are more in the price range of typical western oil stones. Your catalog lists two basic types: the coarse stones (Toishi) and the finish stones (Shiage Toishi). What's the difference between these two types? What are they made of?

Woodline: Well, there's a variety of material used to make the man-made stones. The coarse stones, we believe, are made of



aluminum oxide which is fired in an oven to form a brick. In fact, that's just what they amount to ... a brick made of very fine material.

As for the man-made finish stones, there are a lot of different ones made, and it's difficult to determine what material is used. We do know of one stone that's made of cerium oxide — that's a rare polishing compound, the stuff that's used to grind mirrors to make telescopes.

It's difficult to say what all the stones are made of because the stone people, the manufacturers, won't tell us what materials they use.

Woodsmith: How would you compare Japanese water stones to western oil stones ... to the Arkansas stones for instance? Woodline: Arkansas stones will give you a really fine finish, but they won't polish the edge as finely as the water stones.

Personally, I think there are two problems with Arkansas stones. First, they're never flat. Even after they're flattened, it doesn't take much sharpening before they become dished out. And second, the Arkansas stones are so hard you can't feel the tool on the stone.

The water stones are softer. Part of it is just individual feel, but if you have a softer stone that's cutting a little faster, you can feel the tool on the stone and it helps you find the bevel.

What happens with the Arkansas stone is that the material on the surface becomes rounded, which reduces the cutting action. Until you wear that surface away, you're not exposing any new abrasive.

The water stones on the other hand, are softer material. You're constantly wearing away the top abrasive particles and exposing the fresh, sharp abrasive underneath. The end result is that water stones will cut much faster than oil stones. Woodsmith: When we decided to get some water stones, the first problem we had was trying to decide which stones to purchase for a coordinated sharpening system. What stones would you recommend to achieve a very fine edge on western tools? Woodline: There are a couple of ways to go about it. For the coarse stone, I'd recommend either the 1000-grit King stone, or if you have a tool that's in relatively good shape without any nicks, you can use a 1200-grit King stone.

Then there are two choices for finish stone (Shiage Toishi), which is determined pretty much on your budget. The 6000-grit King S-l, or if you want an even finer finished edge, the 8000-grit Gold stone. Woodsmith: Can you go straight from either the 1200, or the coarser 1000 King brand, directly to the finish stones? Woodline: Yes you can, but I personally think using the 1000-grit stone will leave the edge a little on the rough side. You'd be better off to go with the 1200-grit King stone, which produces smaller scratches on the bevel, and then go to the finish stones, either the S-l or the Gold stone.

Now if you want the keenest, finest edge that you can get, I'd use the coarser 1000-grit coarse stone for a faster sharpening, to remove nicks, and follow it with what we call the blue stone (Ao Tosihi, a natural stone), and then the finish stone. The blue stone takes out the scratches of the coarser 1000-grit stone fairly rapidly, and will allow you to get a better finish and a longer lasting edge with the finish stones. But a lot of western tools are simply not worth the effort because one swipe, and the edge is gone anyway. Woodsmith: We've been using the King brand 6000-grit S-l as our finishing stone. We've considered purchasing the 8000-grit Gold stone, and were wondering how much it would really improve the edge over the S-l?

Woodline: Well there is a difference. They're different materials for one thing, although the manufacturers won't tell us what the material difference actually is. The Gold stone is a harder stone and it gives a faster polish than the S-l. But I don't care for the Gold stone quite as much as I do for the S-l, even though I think the

Gold stone gives a little better edge. I still prefer the S-l because personally, I like a little softer stone.

Woodsmith: After the stones are in hand, what steps have to be taken before they're ready to be used?

Woodline: The very first thing is that the stones have to be wet. . . they have to be well saturated. I keep my stones in a bucket with a tight-fitting lid so they stay damp. Then when I'm ready to use them, I fill the bucket with water and by the time I'm ready to go, the stones are saturated. Woodsmith: Can the man-made stones be left in water indefinitely? Woodline: All of the King brand (man-made) stones that we carry in our catalog can be left in water. Here in the shop we have stones that have been in water constantly for six years, and there's no ill effect. There are other brands of man-made stones that cannot be left in water because part of the compound in the stone will be leeched out, and then they won't sharpen properly.

One other thing. We used to have a problem with scum if the stones are left in water all the time. But a couple of drops of Clorox took care of that. And I mean just a couple drops and no more, or it stinks up the water.

Woodsmith: You said the King man-made stones can be left in water. How about the natural stones?

Woodline: No! It should be made clear that the natural stones will come apart if they're left in water. I don't think the natural blue stone will, but all of the other natural finish stones will.

I'd suggest your readers check with whomever they bought the stones from to find out if it's safe to leave them in water. Woodsmith: Once the stones are saturated, what's the next step? Woodline: The next step is to be sure that the stones are flat. For the coarse stones, the easiest way to flatten them is to rub them on a piece of 220-grit Wet-or-Dry sandpaper that's on a flat surface. Woodsmith: Using water as a lubricant? Woodline: Yes, put the sandpaper in some water to get it wet or just throw a little water on it before starting to lap the stone. The ideal way to lap it is to hold the stone in the center, and push it away from you applying pressure only as you move forward, and let up as you move back.

You don't want to move the stone back and forth with pressure both ways because that tends to round over the ends. Then turn the stone end for end, and take a few more strokes. It depends, it may only need a couple of strokes.

Then the next step is to make sure that the edges, which may be sharp at this point, are sanded at a 45° angle. It only takes two or three passes on each edge. The reason for beveling the edges is to keep them from chipping off under the pressure of the tool as it reaches the edge of the stone.

Woodsmith: Do you use the sandpaper method to flatten both the blue stone and the finish stone?

Woodline: No, never. Both the blue stone and the finish stone are flattened with a coarse stone that's already flat. The finish stones are soft enough that if you get carried away rubbing them on the sandpaper, you'll wear away a year's worth of abrasive.

Woodsmith: Once the stones are flat, what are the steps involved in sharpening a plane iron or chisel, for example? Woodline: Actually, the first step should be to square up the edge of the plane iron. On western planes irons, if they're really bad, you might want to go to a grinder to square up the edge. But with a Japanese tool, you simply cannot put it on a grinder because even very low heat will draw the temper. Once you've got the edge square, the next step is to flatten the back on a coarse water stone.

Woodsmith: I've noticed when honing on the coarse stone, a kind of slurry builds up. Are the water stones supposed to create a slurry on the surface? Woodline: Yes, the coarse stone creates its own slurry as the tool is being honed. As the slurry builds up on the surface, leave it on the stone. What happens here is that the particles get finer as the honing progresses. As those particles break down, they begin to refine the edge. Woodsmith: So it begins to refine the edge even before switching to the finish stones? Woodline: Yes, because you've got a finer material in suspension. If you have a lot of heavy removal to do, you may want to clean off some of the slurry on the coarse stone to get back to the coarser grit. But when you're finishing up on the coarse stone, you definitely want the slurry left on the stone to refine the edge and get it ready for the next finer grit stone. Woodsmith: So once the back is flattened on the coarse stone, do you move on to one of the finish stones?

Woodline: Yes, after the back of the iron is flattened, it's polished on the finish stone. But before the finish stone can be used, it's best to bring up a slurry or mud using a Nagura stone. Move the Nagura in a circular motion over the stone to bring up some of the abrasive compound and put it in suspension on the surface of the stone.

The honing process would eventually accomplish the same result as the Nagura, but using the Nagura stone just speeds up the process. This slurry is what actually does the polishing. So you never want to remove the slurry — even if it starts to turn dark from the metal of the plane iron. If it starts to dry out, just add a couple of drops of water.


Woodsmith: One question we had after experimenting with the water stones is how much water should be used? Woodline: You only need to use enough water to keep the surface lubricated so that you'll have a smooth feel with the tool on the stone. When it starts to dry out, I usually dip my fingers in the water and shake a couple of drops on the stone. Woodsmith: So you're not trying to water down the creamy paste that accumulates on the surface of the stone. Woodline: No. The idea is that you don't want to keep flooding the surface, but to use just enough water to keep it well lubricated. And that will also vary from tool to tool, depending on the hardness of the steel and the width of the bevel, etc. Woodsmith: Once the back of the iron is polished on the finish stone, what are the steps in honing the bevel? Woodline: The first step is to hone the bevel on the coarse stone until you've turned a wire edge. Once the wire edge is turned on the coarse stone, you alternate honing the bevel, and then the back on the finish stone. I usually take about 5 or 6 strokes on the bevel for each stroke on the back.

Woodsmith: You only use the finish stone to remove the burr?

Woodline: Yes, once you've turned a wire edge, you don't wipe the wire edge off on the coarse stone, it's only taken off on the finish stone.

Woodsmith: If you're using the blue stone, do you use it after the coarse stone to hone the bevel, before going to either the S-l or the Gold stone?

Woodline: Right. Then you alternately hone the bevel and the back until the wire edge is removed.

Woodsmith: After the wire edge is removed on the blue stone, then you go straight to the King S-l stone to polish the beveled edge? Woodline: Yes.

Woodsmith: How can you tell whether or not you're improving the edge on the finish stones if you've already removed the wire edge on the blue stone? Woodline: As you hone the tool on the S-l or the Gold stone, you inspect the bevel. And you can tell because it becomes polished.

Woodsmith: So you use the level of polish to determine the sharpness of the tool? Woodline: Yes, the level of polish tells you where it's at. Another thing you'll find when sharpening Japanese tools is that the wire edge comes off faster than on western tools.

Woodsmith: Is that because the western steel is softer?

Woodline: Exactly. We've tested some Japanese plane irons that are 65 or a little higher on the Rockwell scale versus English tools we've tested that are 54 to about a high of 61. And that (the Rockweli scale) is not a linear scale; it's a logarithmic scale, so there's quite a bit of difference in hardness of the steel between Japanese and English tools.

Woodsmith: Let's say I had a lot of money to spend, would you suggest getting some of the natural stones? Woodline: I don't think the natural stones are worth the price ... for Western tools. Except for the blue stone (Ao Toishi), which is a natural stone. It definitely gives a better finish and a longer lasting edge because it removes the scratches left by the King brand coarse stones. Woodsmith: With all of the advantages of water stones, what would you consider to be their drawbacks?

Woodline: The only drawback would be in using water. I sharpen on the floor, so it's not much of a problem. But if you were working on a bench, and you get water on the wooden bench, it would have to be considered a drawback. Woodsmith: How about in terms of actually using water stones to sharpen? Are there any disadvantages in comparison to western oil stones.

Woodline: As for my personal feelings, there are no disadvantages in comparison to western oil stones. And I feel that the water stones make a better sharpener out of you. They cut faster, they're easier to use, and a person usually has better success in using them because you can feel the cutting action.


After talking with Ered Damsen about "coarse" water stones, I think some clarification of this terminology is needed. The 1000-grit King stone (which Fred calls the "coarse" stone) is actually equivalent to a soft Arkansas stone. In effect, Japanese water stones begin where the western oil stones leave off.

As for the Japanese finish stones, the "grit" of these stones is so fine, there's nothing else to compare them to.

opinions. We've been using Japanese water stones in our shop for about six months now, and everybody here is quite impressed to say the least. Even the least expensive combination of coarse and finish stones (1000-grit coarse and the S-l finish stone, about $12 each) can produce an edge that puts a razor blade to shame. And they do it with amazing speed.

Without overstating the case for these stones, I think they're well worth having in the shop. The only probem is deciding which stone (or which combination of stones) to buy.

We've tried several combinations, and to be honest, we've had a lot of difficulty (and several heated debates) trying to determine the "best" combination.

The question finally got down to: How sharp is sharp enough? This may sound strange, but until we tried the water stones, we never thought we could "over-sharpen" our tools.

The edge produced by these stones (especially the finish stones) may actually be sharper than western tool steel can "hold". On most of our western tools, this ultra-edge may be gone in the first pass over the wood.

With that in mind, using a combination of the 1000-grit coarse stone and the S-l finish stone would be an excellent starting point . . . and maybe all that's needed to sharpen western tools.

However, if you're sharpening Japanese chisels or plane irons (which have much harder steel), using the natural blue stone (Ao Toishi) as an intermediate step, and finishing with the 8000-grit Gold stone may make enough difference to warrant the extra expense.

All of this gets down to a matter of personal preference. If this sounds like I'm dodging the issue, to some extent I am. In all honesty, the results of our shop tests are really more proof of our limitations in determining degrees of sharpness, than it is a criticism of the water stones.

The bottom line is this: All the excitement about Japanese water stones is more than justified. Get one and try it out. Your plane iron will love you for it.

tips. As we were testing the water stones, a couple of things proved useful to make the whole process run smoother. First, we used a common dry wall mud bucket to soak the stones. (This is just a plastic trough, available at any lumber yard). It's just the right size for all the stones mentioned in the interview.

Another thing that seemed to make a difference was using the Nagura stone to bring up a slurry on the S-l stone. The Nagura only costs $4.95, and improves the finish the S-l put on our chisels.

And a final note of caution: Don't leave these stones in an unheated shop. If the temperature dips below 32°, the water in them will freeze, and crack the stone.

sources. All of the Japanese water stones mentioned in the interview can be ordered from the Woodline The Japan Woodworker (Catalog: $1.50), 1731 Clement Ave., Alameda, CA 94501. The stones mentioned are: Coarse (Toishi) water stones:

King brand 1000-grit $10.95

King brand 1200-grit $10.95

Natural blue stone:

Ao Toishi $14.50

Finish (Shiage Toishi) (man-made) stones:

King 6000-grit S-l $11.95

King 8000-grit Gold $38.95

The Nagura stone for the S-l finish stone is Stock #15.573.96 — $4.95 The Nagura for the Blue stone and the Gold stone is: Stock #15.576.47 — $3.50.

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