ERU Sharpener: Full review and evaluation

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Jan 19, 2010
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When Fred offered to send me an ERU to test I had a good idea of what I wanted to do with it right away. There are certain materials that tend to dull my favorite knives out very quickly. I mostly use mild and simple steels like 1095, Sandvik 14C28N and recently have been using a really nice traditional pattern from Kershaw that is VG-1. I love these knives and they’re all generally in my everyday carry or everyday use category but I also tried it out on some kitchen knives that I’ve never used and didn’t know the angles for. Just trying to get an idea of how much work and effort would need to be put into restoring an unknown edge from an unknown angle.

But the ERU is the “Edge Renewal Utility” and the renewal portion of that is key here. When you take a very sharp edge into the field and you start using it on something really abrasive, it loses the edge pretty quick--of course I’m talking in my own experience. You start wanting to get every last bit of cutting action out of it before having to go to your field hone because you know you’ll have to spend at least a few minutes just to get a serviceable edge--again your mileage may vary. In any case a lot of people have realized a long time ago that using a strop or a steel to touch that edge up before it gets too bad will keep them cutting for a long time and that’s what I wanted to test this tool for.

Now the basic design of the tool is very simple, but simple ideas are usually the best ones. The ERU is essentially two circular discs with a small quadrant cut out from the center at a 90 degree angle. There are two carbide teeth opposing each other on each circle, and you can set the angle for a very wide variety of tools with this design and at exceptional accuracy and ease. The graduations marked go from 10 degrees ( inclusive ) up to 40 and are marked in 2 degree graduations but it’s very easy to set the edge degree by degree by simply setting half-way between. The lines are clear to read and deeply engraved so I don’t see them wearing out any time soon. Past that it is possible to accommodate blades wider than 40 degrees and using a simple felt marker it’s easy to find the right angle for a blade even if you don’t know the angle.

A key design feature that deserves its own mention is the carbide teeth themselves. A lot of times with these carbide sharpeners, the teeth act as cutting edges on the steel--they’re even angled at such offsets to deliberately attack the steel at an angle. This is not the case with the ERU, where the surfaces of the carbide inserts are flat and smooth, and at a perfect parallel to the bevel of a knife. This creates more of a smoothing and polishing effect than the cutting action associated with traditional pull through devices. I am not sure by what function these work mechanically but from a purely practical standpoint I think it’s comparable to steeling where it’s aligning and smoothing the edge on a harder surface.

The adjust-ability of the angle is also hugely important of course, but I think some other devices try to accomplish this and the smooth surfaces and fail. There are some pull-through type of sharpeners that use stone or ceramic wheels for instance, and they try to remain parallel to the bevel as well. However they don’t have adjustable angles, and on top of that produce a lot of chatter and don’t do an edge much better than the harsh carbide cutting bits of those types of devices.

You can get a good view of the carbide inserts and the tool itself with these pictures. The overhead view of the carbide inserts really shows how they are perfectly in-line with the centerline of that screw. There is a slight bit of risk of torquing the blade side to side, but one would have to be using the tool very, very sloppily for such a thing to happen. As a guy who takes a lot of pride and effort into sharpening, I’m often very meticulous and so I thought “Maybe I’m not the one to judge this.” So I let my friend David use the ERU on my Izula--one of my favorite knives so that ought to show you my confidence--and he is pretty much lacking in the meticulousness or pride in sharpening and more pragmatic. All I was interested in was having him making some cuts, sharpen it to where he felt an improvement, and then see if maybe the “less-than-meticulous” style of use would show some problems but this wasn’t the case.

The whole thing is wrapped up in a pretty handsome package with a great sheath and compact shape. I mean one thing that stands out to me about this tool is that it can go right in your pocket, and come right out and be used whereas a lot of other guided sharpening tools are a lot more complicated to setup. I didn’t think the sheath was really needed at first, but it’s actually pretty useful in giving you a bit of a “handle” for it. Depending on how large your knife is, you’re going to want to hold your fingers a bit lower, and the sheath also acts as a “stop” by turning it around so the knurled screw sits atop the sheath. You wouldn’t want it to suddenly slip into the sheath and it just makes it a bit sturdier feeling in hand. I didn’t have a vise to test it out, but it’s also textured nicely to be able to grip padded vise jaws firmly and stay in place.


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So onto how I tested and what I tested... First things first, I wanted to check out the angle-finding. The manual that comes along with the ERU instructs using a felt marker to find the high and low spots and find the angle by adjusting like this. There’s nothing wrong with this but what I was really curious about was how closely it matched the angles that I believed my knives edges were at, and thought it would be interesting to use it to find the angle of knives I haven’t re-profiled to a known degree yet. The tested knives were of a variety: I had a OXO brand pairing knife, a Kershaw “Needs Work”, an ESEE Izula and another Kershaw “Wild Turkey” traditional pattern. I used the ESEE Izula to do the final “trial” runs but used the ERU on all of these. The Wild Turkey, I wanted to find the angle--and it was a nice 32 degrees--and past that wanted to prove that people should have no hesitation to use “nice” or “fancy” knives in fear of scratching the blade. The Wild Turkey has a beautiful San Mai blade and a nice polish, and the ERU actually made the bevel look more polished and very nice and didn’t leave a scratch on the rest of the blade surface.


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You can see my first bit of testing was basically just checking the angles on knives, and seeing if they matched with the ERU. I use a caliper and trigonometry to find angles of knives and it was pretty quickly established that it was very accurate. I used the pairing knife because I never bothered to measure it using my traditional method measuring the spine from the hone. Anyway, I used the marker trick to determine that the edge on the pairing knife was 33 degrees. I measured the edge thickness at the shoulder and used the width of the bevel’s face and it worked out to 15 degrees per side. I wish I had a laser goniometer because measuring with the bevel thickness and face-width isn’t very accurate, but it’s right in the ballpark so I’m pretty sure it’s dead on. Moving past that to further substantiate it, I knew that my Kershaw “Needs Work” was set at 14 degrees per side ( using a stack of pennies for reference ) so I set the ERU to 28 degrees and it worked immediately. Now I tried to do the same with my Izula but I have a bit of a free-hand edge on it so it was a bit more obtuse than I had previously worked out and the bevels a bit convex, but using the ERU I found it was set to 40 degrees which was only 4 degrees over than my estimate. Okay so moving on past measuring the angles, I’m satisfied they’re dead on and easy to find with a felt marker. Or if you have any experience using a machinist’s protractor to find the angle of a cutting bit I even managed to use it like that to find the angle without the marker.

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What I was more concerned with though was how it actually effected the edge even despite seeing Fred’s pictures. The concern was that because the carbide teeth offset each other, that it would make a “shearing” motion and cause chatter on the edge of the blade. Basically tear it up and leave tiny little “cuts” where the carbide tore bits of steel out. That is how most of those carbide “scrapers” actually work, they don’t do any polishing or anything and so they use a superficial edge that goes away immediately. This was not the case at all with the ERU and I used various scopes and magnifications to make sure of this. Unfortunately I don’t have a USB scope or anything, but at 45x all the way up to 100x the bevel looked crisp and clean. The visible difference with the ERU is that lines formed were now parallel to the edge, and were very polished and smooth. They looked more like small striations on tool parts than grind markings. Very close to what a steeled edge looks like though I’m not willing to suggest it’s the same mechanics, as typically with steeling one holds the edge at a slightly more obtuse angle. But the end result is extremely similar in my opinion.
 
More important than visual observations and speculation and all this pseudo-science stuff... I did some good ol’ cutting tests. Nothing complicated, but using my Izula fresh off my DMT hone as I normally sharpen, hair-whittling sweetness...

-I carved feather sticks out of old, dry seasoned bamboo
-Sliced off 3 bits of denim rolled to 1“ diameter
-Cut 1/4“ nylon rope and continued to whittle dry bamboo until rope was difficult to slice
-Then whittled the bamboo more until the edge could not cut phonebook paper cleanly

Now clearly there’s a lot of subjectivity here but I didn’t really have the supplies or anything to do something more scientifically objective or anything. You’re just going to have to leave it at my own feelings of when it was “dull” at what point, but each time I sharpened with either my DMT or the ERU I took the edge up back to the point where I could do “S” cuts through phonebook paper as shown.

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Now denim might not seem like a big deal, but it dulls knives extremely fast and especially ones with simpler steel. I rarely get a knife to make more than 3 or 4 cuts through it and at that point it’s not so much slicing as much as I’m just cleaving it with pressure. All of these efforts are basically trying to mimic realistic wear, but in an accelerated fashion. My real main concern wasn’t how well it sharpened or how long the edge it produced lasts, but I did want to do something that would at least demonstrate those factors a little bit so I didn’t want to just run the edge up against something hard or extremely abrasive.

Anyway moving on, after I dulled the Izula’s edge that I used the DMT to get, I decided to sharpen using my DMT again and time how long it took. I was basically just going until I could S cut phonebook paper as I said, pausing the timer when I was testing on paper. I then dulled that edge with cutting and it made 3 cuts through the denim before starting to fall as I expected and then I proceeded to just wear it past paper-cutting to have a “dull” edge to renew with the ERU. I then cut again until dull, and using the ERU a second time got it back up to paper-cutting. The reason I did two runs with the ERU is because I’m really accustomed to using my DMT, whereas I’m just kind of cutting use to the ERU and plus I wanted to see if it had any differences in how long it took to renew an edge that has already been polished. Well as I suspected, on the second pass it got it back to paper-cutting much quicker. At this point I doubt I would have seen any improvement in time from one sharpening to the next and really is kind of not testing the purpose of maintaining an edge before it gets too dull. I just wanted to get some kind of benchmark of how long each tool took to go from very dull to very sharp.

DMT-Run -- 7:44
ERU-Run(1) -- 3:38
ERU-RUN(2) -- 2:29

Now an interesting thing happened, and I’m not sure I should comment because of all the variables involved but when I used the edge after the ERU it took a lot longer to dull. Each time in fact, and I have a feeling that the more polished it got the longer it took for the tests I was running it through to fail. Either way, there is a concern that with the gimmicky carbide sharpeners that the edge is superficial and just wears off compared to a “real” edge. Well, at least in this one instance the ERU’s edge outlasted the edge I put on my DMT and again keep in mind that with both tools I was only sharpening them to the point they would “S” cut phonebook paper--no idea if they were “hair whittling” or anything else, I wanted to test practical cutting and edge holding.

Beyond this, I wanted to use it more as intended--or as I would intend. I wouldn’t want to dull a knife as much as I did before restoring its sharpness, so I decided to just cut denim until it didn’t slice easily and I was just “cleaving” and “sawing” it to get through. Then see how many passes I had to do with the ERU to get back to a good slicing action through the material. Denim is some pretty abrasive stuff for some reason and 1095 isn’t particularly renowned for its edge holding, but it did pretty good I think and needed minimal work on the ERU to get back to slicing sharp. I didn’t really count the passes but it was only a dozen or so and much less time than the 2:29. My friend David who I decided to use as a guinea pig seemed to restore a satisfactory “working” edge even more quickly than I when doing similar tests with denim.

If you put this all into practical terms... Suppose for some reason we had to cut as many half inch slices off this denim roll as we could, as fast as we could. We had a whole 24“ roll and can cut about 1.5“ to 2“ before the blade dulls out. Now looking at the times above the first DMT run took 464 seconds, the best ERU run 149 so that’s literally almost a 1/3 of the time and we’re talking about going from DULL to SHARP. When just using each tool to “touch up” and maintain a serviceable level of sharpness I’m still confident the ERU would be much faster even for a skilled free-hand sharpener. Then again maybe I am just a slow free-hand sharpener. So think about that from a practical perspective, even if you know how to free-hand and get a superb edge doing so, the ERU will help you maintain your already-superb edge much faster and more conveniently I believe.

Suppose you’re out in the cold and you’re hands are shaking or you’re just tired. It can be tricky to hold a steady angle on your hone at times, and even worse one wrong move and you’ve just undone all your work and created even more for yourself. It can be a miserable experience trying to free-hand an edge when you’re just having an “off” day and it just won’t happen. I don’t pretend to be the best sharpener in the world but I’m pretty sure this doesn’t happen to just me; some days you just don’t have “it”. The ERU is every single bit a tool to make your life easier and do a good job with no compromise in quality, and it does this both in the craftsmanship of its construction and the performance results of its intended purpose. Classing it in the same league as those “gimmicky” gadget carbide sharpeners is not appropriate because it is not a gimmick, and it’s not a gadget and I can easily see how this would be a tool any skilled craftsman would be happy with. I’m not going to lie and say I don’t prefer my own edges, but if we’re talking about field sharpening devices there are very few out there that I wouldn’t go and put my “normal” edge on after using.

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I didn't get a picture of the S cut after sharpening with the ERU but you'll have to take my word for it. You can see the striations the ERU made, giving it a brighter polish than it actually had before. And as you can see it was able to cut 5 slice of denim!

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As far as using the ERU to restore edges of seriously blunted knives, I think I would sooner get my benchstone out but I think it is possible. I had a very interesting kitchen knife, “EKCO FLINT STAINLESS VANDIUM” so maybe it was a particular hard steel but I just could not get an edge back on it within an hours worth of work. It did make it sharper--I mean it cuts wood and stuff now at least. So I think if a person is looking at this as a way to sharpen and restore seriously blunted knives and , re-establish bevels then there are probably better tools to use. With that being said depending on the level of damage and what is satisfactory to a user, I’m pretty sure most people can get even a not-so-good-to-begin-with edge back with this giving it a little elbow grease.

I do not know if it’s best to use a drawing or pushing motion--that is pulling it in one direction only, or being able to push it forward too. It does work both ways but for the sake of safety I’d discourage working up any kind of “sawing” motion both for you and your blade, especially if you’re holding it by hand. I didn’t have a vise so can’t comment but it seems that if you were a little “crooked” and caught a chip or deformation on the sides of one of these inserts that the results could be a pretty bad snag, and while nothing bad happened to me such things could be somewhat catastrophic--think broken knives and cut fingers. But that’s just a disclaimer... It is a rugged tool and you do not have to be gentle and can really “use” it. As with all things discretion is key.

What I find somewhat troublesome is that if you do try to pull it out, and then set the blade back inside the V you run the risk of hitting the tops of the discs. I think sliding it backward, and then pushing forward with light or no pressure like one would with a file is best and you can even lift it up against each carbide insert in a “steeling” fashion to really refine it more than one might expect. As with any good tool, it can do more than its face value when in the hands of a skilled individual and there are a number of “other” uses I think it’s great for.

As I mentioned being able to use it similarly to a machinist’s protractor, one could actually use it as an angle-gauge. This might not seem that beneficial, but let’s say you DID have a really blunted edge that the apex would just take too much time on with the ERU--it still helps because you can quickly find the angle it is sharpened at and use another tool to grind closer to the already established bevel. Once again another way to save you time and effort, and plus extend the life of your blade by avoiding needless and excessive metal removal.
 
Kenny, great review, I see you were impressed too, thanks for the pics, unfortunately my camera's auto focus and macro settings aren't working correctly.

One thing I wanted to try were some serrated edges like Spyderco's spyder edge and The Christy serrated bread knife serrations. I have no doubt that'll do them as well, I was able to do a single bevel chisel grind on a SOG Mini Auto Clip in BG42, this is some tough steel and when it came to bringing the edge back up to a sharp working edge it was great, if the bevel was really bad I think you'd have a little more work in front of you but the alternative out in the field with regular diamond hones would still be difficult unless you were proficient at maintaining your angle.

I was glad to get in on this pass around, it really changed my original impression of this style sharpener. Thanks again Fred for the chance to check this out and thanks for an excellent review Kenny.
 
Thanks, Ted. Yeah I've really grown a liking for it the few days I've had it... I see why it took so long to get to me now. Saying you were "sick", right :P haha j/k I'm glad to hear it works on steels other than the stuff I had available to test--I'm a fan of simple low-alloy steels, what can I say.
 
Thanks for the review! It sounds more and more promising and I think it is what it is - a handy sharpener on the go, and maybe more. And I can see how useful it is in a situation that you described - cold, wet hands at dusk, tired in need of a sharp edge. Not that this happens a lot though ...
 
Kenn,

Thank you for taking the time to access this new tool. I had you pegged, for someone without preconception or bias and your post confirms this.
As an inventor and a knife maker I find I make better decisions and greater discovers, when my mind has not taken a firm set or bias. It is human nature to do so I know, but in order to move forward its necessary. Above my work table is one of my favorite quotes: "Without deviation from the norm progress is not possible". F.Z.

Regards, Fred
 
Kenny, thank you very much for the very detailed review. :cool: The ERU is now officially on my must-buy list. :thumbup:
 
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