Electric Knife Sharpeners

[Chris Amirault]

Indeed, you can get bolsters ground down by any machine shop or grinder for dirt cheap or free. I have a 25-year-old Wusthof that I took to a grinder for this very purpose a year or so ago. Smart move.

[Anna N]

. . .

I was absolutely astounded with the results. In just a few seconds, with little effort and less skill, I got better results than I get with a stone. A very sharp, smooth edge -- at least by the standards of an amateur sharpener like me. Was it a samurai sword? No. Did it come out as sharp as if Chad Ward had sharpened it, or that guy at Korin, or even the average Edge Pro aficionado? Not likely. But it cut an onion like nobody's business.

. . . .

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"But it cut an onion like nobody's business." With this you have hit the nail on the head for all us owners of electric sharpeners. Dammit - we don't need samurai swords. Thank you.

[Fat Guy]

Indeed, you can get bolsters ground down by any machine shop or grinder for dirt cheap or free. I have a 25-year-old Wusthof that I took to a grinder for this very purpose a year or so ago. Smart move.

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A capital idea. I can probably keep my Wusthof chef's knife going for 100 years this way, until it is a paring knife with a very big handle. Now how the heck do I find such a place in Manhattan?

[Fat Guy]

I've been trying to figure out a way to take some useful photos. Camera didn't work so well so I tried my scanner, which also didn't work so well.

Anyway, here's the Sabatier knife I used for my first attempt:

Here's a closer view:

And here's the closest view I was able to get:

I think it's possible to see the two strata of the edge -- the coarse-ground one topped with the fine-ground one. You can also see I need some practice with the machine to get them a little more uniform where the blade curves. Still, this edge works very well indeed. You can also see it's a fairly smooth edge. And it's not like the machine takes off a ton of metal. It's only going to be significant over a period of many years, I imagine.

[Fat Guy]

I was thinking the knife was a little sharper than when I do it by hand on a stone. I chopped an onion and it felt a little sharper. I carved up a leftover turkey breast and it felt a little sharper. I cut some salad ingredients and it felt a little sharper. But today I sliced up some Citterio Abruzzese dry sausage and realized the knife is a lot sharper. Which may be an equivocal statement, given that I'm not the most talented by-hand sharpener. Still, I've got to figure that I'm better at it than 99% of the population, so if the electric sharpener offers an improvement over what I can do by hand then it's certainly a good general-use product.

[Fat Guy]

Tonight the knife passed the ripe tomato test with flying colors. No this wasn't a vine-ripened August tomato, but it was pretty soft after about 8 days on my kitchen counter.

I am so pleased with the electric sharpener that I am reevaluating my future knife-purchasing plans. I think I'll simply go with bolster-free knives from here on in. I've been meaning to pick up a 24cm Tojiro-DP Gyutou, and I think this is the push I need.

[maggiethecat]

I too am committed to knives sans bolsters since we acquired our electric knife sharpener. In fact, I'm taking it to Canada over Christmas so that I can sharpen all my father's knives.

[Octaveman]

Tonight the knife passed the ripe tomato test with flying colors. No this wasn't a vine-ripened August tomato, but it was pretty soft after about 8 days on my kitchen counter.

I am so pleased with the electric sharpener that I am reevaluating my future knife-purchasing plans. I think I'll simply go with bolster-free knives from here on in. I've been meaning to pick up a 24cm Tojiro-DP Gyutou, and I think this is the push I need.

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I for one will be interested in your results as the Tojiro is much harder than your Sabatier so hopefully it won't end up a finely serrated knife from all the chips. You may want to consider a Togiharu as they are marginally softer and may hold up better with your sharpener than Tojiro. Do you know what grit level the grinders are on your sharpener?

On a side note, the Messermeister Meridian Elite is bolsterless and from what I hear quite good as far a Euro knives go.

[Fat Guy]

That will be an interesting experiment, then. I guess worst-case scenario is I take the damaged blade to Korin and they fix it up.

How does it compare in hardness to my Wusthof?

[slkinsey]

Significantly harder than the Wusthof.

[Octaveman]

Yes, the Tojiro is much harder. I'm not 100% sure but I think your knife is likely about 55-56 HRC whereas the Tojiro is around 61. The Togiharu knives are about 58-59 so their closer. The Togiharu Molybdenum is reasonably priced like the Tojiro but much softer. I personally feel the Tojiro has a better blade but Togiharu has better F&F.

I looked at the description of the sharpener you have and what you've told us in your posts. I think you might be okay if you don't hit the course grinder in order to minimize chips. But hardness is only one part of the picture. Japanese knives are much thinner too so there's less metal at the edge to handle the harsh grinding. Plus, it's my guess your sharpener's angles are very obtuse given the small bevel it created as seeni in your pics. With the acute angles of pretty much every Japanese blade, the sharpener would just eat up the edge. That is, at least until the original edge is gone. Then you've just made a German knife out of a Japanese knife albiet with better material. I've long heard that electric sharpeners are no good for Japanese knives despite the fact that Shun makes one. But if you're willing to give it a shot, I'm willing to watch

Edited December 8, 2008 by Octaveman (log)

[Fat Guy]

The literature says "Grinds at optimum angle recommended by knife manufacturers (18 to 22 degrees)." I wonder if that means 22 for the coarse and 18 for the fine. How would that differ from the recommended angles for a double-edged 50/50-balanced Japanese knife?

[slkinsey]

It seems likely to me that this means they are doing a double-bevel, with the coarse wheel grinding it down to an 18 degree back bevel, and the find wheel putting on an edge bevel at 22 degrees.

A 22 degree bevel (44 degrees included angle) is not particularly acute. Japanese knives are sharpened to a much more acute angle than that. Something like 14 degree bevels (28 degree included angle) wouldn't be unusual for the Tojiro-DP Gyutou.

Edited December 8, 2008 by slkinsey (log)

[Octaveman]

I could be wrong but my guess is that the 18* refers course grinder as that would create the wider bevel then the 22* would be used to create the actual cutting edge. This would be similar to a micro bevel being created. If I do a micro bevel on the stones I raise the angle a bit. This would make the edge stronger.

As far as desired angles, if the degrees given were combined then I would say, right on. But my guess is that they are degrees per side which gives a combined angle of 36-44 degrees. That's HUGE. Most Japanese knives will have at most a combined 25-30 degrees or 12-15 per side. When I sharpen on stones I will go lower than that depending on the knife and it's purpose. I just sharpened a friends DP and it had a pretty acute angle on it from the factory so 10-12* per side is a reasonable estimate. Also keep in mind that pretty much all western Japanese knives are 70/30 or 80/20 ground. Making your edge a 50/50 will not pose much of a problem because those assymetrical angles are ground from spine to edge, not just at the edge.

[Octaveman]

I'd be really curious to know grit levels of the two stones and the stropping wheel. If you can take a macro shot of the edge that would help. Or you can look through a jewelers loop and tell us what you see...deep grinding or fine grinding. At 1k the bevels look pretty smooth. I have this feeling though that the course is near 200 and the fine is near 700. Maybe send them an email to see if they come back with something of value?

Edited December 8, 2008 by Octaveman (log)

[Fat Guy]

I've sent an email and I'll see what I can do about a macro shot. You're also free to borrow the thing if you'd like to test-drive it. (The again you're in California!)

[Octaveman]

Um, thanks for the offer but I'll wait to see what happens to your knives first. Yeah, I'm in California where I think it's going to be a blistery 65 today. It should get back to normal in a few days.

Hope they provide some valuable info. Thanks for checking on it.

Edited December 8, 2008 by Octaveman (log)

[Fat Guy]

Also keep in mind that pretty much all western Japanese knives are 70/30 or 80/20 ground.

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The Tojiro is 50/50 according to the Korin website.

[Octaveman]

It's wrong. Unfortunately, it's quite frequent that misinformation is posted on websites. Specially when it comes to HRC values. I checked out what you saw on Korin's sight. I'm skeptical about how it's presented. If I was to read this I would think that are saying it's 50/50 to further emphasize the double beveled aspect rather than actual grind. Not that I'm saying that online retailers intentially mislead the public but there is a lot of hesitance in the minds of the general public with regard to Japanese knives that they try to ease those minds best they can. If they advertised it was a 70/30 grind most people would say "what the hell is that?" and buy something else. In reality though, a 70/30 grind on a knife where the spine is 2mm going down to .7mm right behind the edge is so imperceptable that I can almost gaurantee nobody would notice. To prove my point, a 50/50 grind of .7mm would be .35mm per side where as a 70/30 grind would be .49mm/.21mm respectively. I seriously doubt anyone when cutting away at veggies will be able to detect a .14mm difference in either direction.

I'll ask my friend to bring his knife to rehearsal tomorrow night and I'll confirm the grind for you. There's a simple test to estimate the grind too. Take a pencil and put it up against one side of the blade near the bolster (push with one finger on the pencil at the spine). Make special note of the gap between the blade and pencil at the edge or along the side of the blade. Do the same on the other side. The gap would be the same width for a 50/50 ground knife or wider/smaller for an assymetrical blade. Not scientific but it's a good down and dirty visual check.

[Fat Guy]

I'm eager to learn the truth, though I have a lot of faith in Korin. If you look at most of the other double-edged knives on the Korin site it offers a left-handed option, but on the Tojiro page it says "Blade: Double-Edged (50/50 balanced)" and "Knives with a 50/50 balanced, two-sided blade do not need to be altered for left-handed use."

I have to play with the machine more. I'm wondering if it's really necessary to use the machine's angles or if with the aid of a spacer (or freehand) one can do steeper angles.

[Fat Guy]

Looking at the machine there seems only to be a little wiggle room. But there is a little. I wonder how much I can alter the angle just by leaning one way or the other.

[Octaveman]

If you can play with the angles then that would be cool. Certainly a steeper angle on a Japanese knife would be advisable.

The assymetrical aspect of Japanese knives is not just at the edge or even 10mm from it. The entire blade is ground that way from spine to edge. What Korin speaks of when it says it can alter a knife to be 50/50 ground or even change it to left handed use they are referring to the last 5-10mm of the blade. It would be impossible to completely adjust the grind of the entire blade for left handed use without destroying the blade. I could be wrong with this because I said just about every Japanese knife was assymetrical so I left room for the odd ball of the bunch. If they make it symmetrical then it's certainly not standard. I'll have more info on two DP's tomorrow night. I'll take pics too.

[Octaveman]

I forgot that I still had my friends Honesuki and petty here to sharpen. I took the liberty of at least checking these for geometry. The petty was so damn thin it was very hard to see the heel but given my best estimate it appeared to be 50/50 give or take a little. But again, that thing was THIN so very hard to tell for sure. The Honesuki is without question damn near 95/5. The pics below show what I mean. I also added a few shots of the bevels I created on this knife. I changed the angles I sharpened to be a little more obtuse than originally made. Mainly because I didn't want to risk scratching the hell out of the front side to keep it the same. I changed it to an roughly a 70/30 bevel at the edge. I go by feel so it's more or less that ratio.

The backside of the knife (left side as you hold it aka inside)

The front side (right side or outside)

Another picture of the geometry. You can clearly see that the assymetrical aspect of the blade comes from the spine down, not just at the edge. In order for Korin to change this to a left handed knife, Master Sugai would essentially grind about 5mm of the bevel in the opposite direction that I did which kept with the original assymetric design shown below in the last two shots.

Here is the front side bevel which is about 2.5mm-3mm wide.

The back side at about 1mm wide

Edited December 9, 2008 by Octaveman (log)

[Octaveman]

So tonight I checked not one but two 240mm gyuto's and both were 50/50. They were very thin too as far as Japanese production knives go.

[Octaveman]

I've sent an email and I'll see what I can do about a macro shot. You're also free to borrow the thing if you'd like to test-drive it. (The again you're in California!)

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Did they get back with you?