This is part of a series of blog posts – looking into the appearance and composition of commercially available sharpening stones. If you are interested in the previous episodes, check out the archive for them.

If you have some suggestion on what I should look at next, or want to share your super secret DIY stones, I could be persuaded to open the bag of analytical devices… hit me up on Instagram under @marvgro for that.

Disclaimer: I’m not for sale. Every review you see on this blog is bought with my own money. I have no affiliation to any manufacturer.

Review

Todays sharpening stone is something I have been looking forward to since I heard the announcement – and immediately ordered one. It’s the first stone from fellow sharpener and youtuber “Edge Works Knife Studio”. According to him, the stone is a zero compromise, finely tuned resin stone, which delivers the results and feedback he has been looking for in a stone. He sells them for a very affordable price from the US, and was an absolute pleasure to do business with – clear communication, proactive emails and in my case also a very friendly solution to shipping his stone overseas. I think this is the definition of someone starting a small business and doing very, very, very well in it, which is why I mention it.

Today’s stone is the #1000 grit, which is “the one stone to buy” (heavily paraphrased). It’s a resin bonded stone – on popular demand here are 2 photos of it:

Photos of the EdgeWorks Resin bonded diamond stone “as delivered”. The base looks to me like media blasted aluminium. The resin layer is bonded to it via some intersecting elements. The stone is a light green colour.

Let’s take a look under the optical microscope!

Optical micrographs of the stone. Instrument: Marvscope

The green colour is confirmed further in the optical microscope. We can make out some clustering of particles – some of a very dark, grey colour, some of a deeper green then the surrounding matrix.

Let’s take a closer look in the SEM:

SEM micrographs of the stone. Instrument: Zeiss GeminiSEM 560.

The stone shows a typical, slightly friable resin bond. There is a plethora of different abrasive grains inside it – some very small ones, but also some larger and a lot of medium sized grains. The very largest grains do show a standard diamond morphology, whereas the medium sized ones are closer to silicon based abrasive grains.

Chamberscope view of the stone inside the SEM.

Something I often check with stones, but mostly with natural stones is whether they show any cathodoluminescence – most don’t, but this one does:

VPSE Sensor image of the stone with 0V bias – showing slight catholuminescence. Cool!

Is it important? No. Is it very cool that some parts of the stone emit light when hit with high energy electrons? Heck yeah.

Let’s look at the chemical composition! For this we are going to use an advanced SEM technique called EDS. If you want to know more about this, I’ve written extensively about SEM microanalysis here on this blog.

EDS analysis of the resin stone. Instrument: Oxford Ultim Max  ∞ 40mm² EDS sensor. Note that our EDS sensor doesn’t show elements lighter than boron.

The stone shows a relatively typical composition for a chinese resin stone. We can see some diamond, but also lots of “secondary abrasives”, that are supposed to make the bond firmer. In hand sharpening, these Si, Al and Mg based oxide and carbide ceramics add a lot of feedback – the blissful, constant vibration you experience is caused by these grains. Moreover, this stone contains a surprising amount of titanium – probably mostly in the form of titaniumoxide, which is often found with the other oxide ceramics. There is quite a bit of chromiumoxide, too – which explains the green colour of the stone.

Zooming in a bit closer, the EDS highlights some issues with the mixing of htis stone – the diamonds tend to agglomerate a little bit. This likely will result in larger-than expected scratches and maybe even some raggedness to the cutting edge.

In order to evaluate the sharpening performance and material removal mode of this stone, a blade was sharpened with it. I am using a standardised testing procedure, read about it here. Nevertheless, it’s 65 HRC M398, and sharpened to 17 DPS with resin bond diamond stones down to 10 µm. As this is a Benchstone, I sharpen using a Katocut Nowi Pro, so that the angle is kept constant and my skill is not the defining characteristic in the result. Afterwards, the tested stone is used. No pressure is applied but the weight of the blade. Moreover, the same approach is repeated with a blade in NitroV at 59-60 HRC.

The edge is then analysed in the electron microscope for breakouts and morphological appearance.

Let’s start with the harder steel – the M398 blade:

SEM micrographs of the M398 edge finished with the resin stone. Instrument: Zeiss GeminiSEM 560

The stone seems to struggle a little bit with the high carbide content M398 – we can see that the apex is deformed and folded towards us. This would feel to the “thumb test” like an easily detectable burr – but actually is more akin to some damage to the apex. I applied very little pressure on the finishing passes – the weight compensation of the Katocut was adjusted accordingly. The bevel itself is quite smooth – surprisingly so for a #1000 grit stone. Magnifying a bit further, we can see some slightly deeper scratches – but also that the whole surface gives a plastic-deformed look, with lots of prows and micro burrs formed near the trails of the abrasive. This is a clear sign of a dominant burnishing action – which typically gives a nicer, glossier finish, but less of a well refined apex.

Close up SEM micrograph of the M398 bevel. Note the burr and prow formation near the tracks of the abrasive. Ignore the dirt on it. Instrument: Zeiss GeminiSEM 560.

Optical micrograph of the M398 bevel. Instrument: Marvscope

This is visible in both the optical micrograph, but also the 3D surface scan. The slightly folded over cutting edge is visible:

3D surface height map of the M398 Bevel. Instrument: Zygo NewView 9000, Objective Lens: 20X. Metrological filter chain: LS-Plane to orient data, cutoff 0.1/99.9 percent to remove outliers.

With the surface roughness parameters being very low – as expected after seeing the burnishing effect.

Sa	0.0639	µm
Sq	0.1081	µm
Ssk	7.114	–
Sku	278.8	–

ISO 25178 surface roughness parameters. S-Filter: 2.5 µm (gaussian), L Filter: 0.25 mm (gaussian). No F operation besides LSQ leveling.

Let’s take a look at the NitroV edge:

SEM micrographs of the NitroV edge. Instrument: Zeiss GeminiSEM 560

The NitroV edge looks much cleaner. This steel is not only much softer, but also has less of a carbide content. The stone seemed to have an easier time with this one – proper cutting and a refined apex was achieved.

Optical micrograph of the NitroV bevel. Instrument: Marvscope

The surface morpholgy reflects this in the optical micrograph, albeit some “toothiness” to the edge is visible. This is something most kitchen knives sharpener are looking for – and this also seems a major point for what this stone was developed.

3D surface height map of the NitroV Bevel. Instrument: Zygo NewView 9000, Objective Lens: 20X. Metrological filter chain: LS-Plane to orient data, cutoff 0.1/99.9 percent to remove outliers.

The surface roughness is slightly higher than on the M398 bevel – which was expected, seeing how the stone exhibited less burnishing and more clear cut tracks.

Sa	0.08539	µm
Sq	0.1120	µm
Ssk	-0.2279	–
Sku	4.489	–

ISO 25178 surface roughness parameters. S-Filter: 2.5 µm (gaussian), L Filter: 0.25 mm (gaussian). No F operation besides LSQ leveling.

The stone itself has a smooth, but noticeable feedback. It is immediately obvious, that someone who is a skilled manual sharpener and cares a lot about “feedback” helped adjust the formulation of this stone. If you are into kitchen knives, and freehanding, I think this stone is a very good choice. Pleasant to use, quite fast cutting, good working edge and a very fair price (at the time of this review, about 120$). I feel like it could be improved by more care in the manufacturing process – a bit better mixing, increased diamond concentration to perform better in “super steels”, while hopefully not loosing out to much of it’s feedback for freehand sharpening.

It’s a good stone for kitchen knives, and a nice project from someone who cares deeply about sharpening and the knife community. I think you could do a lot worse, and in this price range there are not a lot of options where you could do better. My biggest issue with this stone is – they are not made in America. Which is a given at this price tag, but for me, who cares deeply about manufacturing in the western world, it pains me a bit.

This is part of a series of blog posts – looking into the appearance and composition of commercially available sharpening stones. If you are interested in the previous episodes, check out the archive for them.

If you have some suggestion on what I should look at next, or want to share your super secret DIY stones, I could be persuaded to open the bag of analytical devices… hit me up on Instagram under @marvgro for that.

Disclaimer: I’m not for sale. Every review you see on this blog is bought with my own money. I have no affiliation to any manufacturer.

Review

Today’s sharpening stone is a bit of an unusal one – in terms of: I look at an abrasive, but also the mechanism used there. It’s probably the most popular sharpening mechanism currently sold in my home country – a Horl 3 Rollschleifer. At the time of the review, it retails for roughly 170 Euro (200 dollar), which is quite pricey for a sharpening device that targets a non-hobbyist group.

It is a rolling barrel. The idea behind it is:

You have a wedge with some magnets, which holds the knife at a fixed angle. Then, you have the abrasive fixed in circular form to the barrel, and roll it along the edge.

According to Horl, the abrasive side consists of extra blocky diamonds, and there is a “deburring/polishing side” as well.

Let’s take a look at the abrasive under the optical microscope!

Optical micrographs of the stone. Instrument: Marvscope

We can see a densely packed electroplatd diamond side. The distribution of the grains looks relatively homogeneous, and they are of standard shape. I cannot support the marketing argument that it’s a very blocky grain – to me, it looks absolute standard micro grit powder.

The deburring side is clearly some ceramic compound, with some darker particles embedded that have a metallic sheen. Interesting!

Let’s take a closer look in the SEM:

SEM micrographs of the EP side of the Horl. Instrument: Zeiss GeminiSEM 560.

The grain size is not super tight – we can see a wide spread between 50 and 80 µm. The grains are embedded in a smooth metallic binder, with the “proper” covering – meaning most grains are embedded about half, which is what one usually aims for in quality electroplated abrasives.

Quite a bit more interesting is the second side, the oxide ceramic deburring stone:

SEM Micrographs of the deburring Side of the Horl. Instrument: Zeiss GeminiSEM 560.

From the morphology, I am near certain that this is created via thermal spraying – the molten, impact like look is quite distinct. Interesting! I guess it is a very workable approach to coat a round workpiece with a thin layer.

Let’s look at the chemical composition! For this we are going to use an advanced SEM technique called EDS. If you want to know more about this, I’ve written extensively about SEM microanalysis here on this blog.

EDS analysis of the EP side. Instrument: Oxford Ultim Max  ∞ 40mm² EDS sensor. Note that our EDS sensor doesn’t show elements lighter than boron.

The EP side, just as the morphology suggested, doesn’t have any surprises: A standard, nickel based EP binder.

EDS analysis of the deburring side. Instrument: Oxford Ultim Max  ∞ 40mm² EDS sensor. Note that our EDS sensor doesn’t show elements lighter than boron.

The oxide ceramic side is revealed to be a standard thermal spraying compound – mostly aluminium oxide, with a bit of titanium oxide and calcium oxides in it.

Sharpening Performance

This review differs a little bit from others – no pre working was done on the blade, it was just sharpened with the sharperner and the included two abrasives. I only used the NitroV blade (59-60 HRC) for this review – geometry constraints! I sharpened 5 cheap kitchen knives to get used but also break in the abrasive – just as the manufacturer suggests.

The edge is then analysed in the electron microscope for breakouts and morphological appearance.

SEM micrographs of the NitroV edge. Instrument: Zeiss GeminiSEM 560

The edge shows some clear rounding over. The scratch pattern is very inhomogeneous, due to the rotating nature of the device, and shows the typical, much deeper gouges created by grains that stick out. The apex itself shows some waviness and a number of deeper dips – I would guess that some larger grains ploughed through there and created the recesses.

Optical micrograph of the NitroV bevel. Instrument: Marvscope

This observation is mirrored in both the optical micrographs, but also the white light interferometer height map:

3D surface height map of the NitroV Bevel. Instrument: Zygo NewView 9000, Objective Lens: 20X. Metrological filter chain: LS-Plane to orient data, cutoff 0.1/99.9 percent to remove outliers.

The surface roughness of the bevel is correspondingly high:

Sa	0.4508	µm
Sq	0.5858	µm
Ssk	-0.4068	–
Sku	3.813	–

ISO 25178 surface roughness parameters. S-Filter: 2.5 µm (gaussian), L Filter: 0.25 mm (gaussian). No F operation besides LSQ leveling.

The aluminium oxide side smooths over the scratch marks, giving the bevel a slight gloss:

Optical micrograph of the edge after using the deburring / polishing side of the Horl. Instrument: Marvscope.

Overall, I’m very torn. The device is super easy to use. It’s relatively compact, which means it’s easily stored in a kitchen. The positives end round about there – in my opinion, the sharpening result is very bad. There’s clear rounding of the apex, the scratch pattern is very inhomogeneous due to the movement of the grain. The lifetime of the abrasive will be limited – especially if one sharpens a high tech steel. I think every reader of my blog knows how quickly electroplated stones wear out – which is typically fine, as they are very affordable. The EP side is available individually for the Horl, as a replacement. In my domestic market, it costs 69 euros – which is frankly atrocious for the amount of abrasive on gets.

The angle wedge has some soft rubber above the magnets, which makes the whole fixturing very pliable – the result is the mediocre apex shape. Moreover, due to the shape of the sharpener, it is impossible to reach into the ricasso on most knives.

Will it sharpen a knife? Yes. But not exceptionally, and I would go so far and say not even “good”. In my opinion there are many better choices out there – any cheap guided system should give you better edges and a system where you are not locked into the manufacturer, but can choose the abrasives freely.

This is part of a series of blog posts – looking into the appearance and composition of commercially available sharpening stones. If you are interested in the previous episodes, check out the archive for them.

If you have some suggestion on what I should look at next, or want to share your super secret DIY stones, I could be persuaded to open the bag of analytical devices… hit me up on Instagram under @marvgro for that.

Disclaimer: I’m not for sale. Every review you see on this blog is bought with my own money. I have no affiliation to any manufacturer.

Review

Yes, I know. “Another Jende”? Yes. I spend a year somehow avoiding the Jende stones in my reviews, then ordered multiple in one go. Be sure to check out the reviews for the “big brothers” – the 120 µm, which I found to be quite good, and the 30 µm one. Today, we’re dipping down to the finest of the stones – the 1 µm Jende diamond resin stone.

Let’s take a look under the optical microscope!

Optical micrographs of the Jende 1 µm resin stone. Instrument: Marvscope

The stone is a light green colour, and pretty homogeneous. Some darker, quite a bit larger particles can be made out. My NA 0.3 objective lens does not have the resolving power to make out individual 1 micron grains – what we are seeing as grains is agglomerates of resin but also diamond grains. This is revealed when we take a look in the SEM:

SEM micrographs of the Jende 1 µm resin stone. Instrument: Zeiss GeminiSEM 560.

In the 30 µm jende resin stone review, I already commented on the amount of non-diamond abrasive grains. Unfortunately, this is something that the 1 µm stone suffers from – but, as we will later see, to even larger effect. Unfortunately, the stone suffers from some amount of agglomeration, where the diamond clumps together. Furthermore, diamond-resin grain adhesion doesn’t seem to be that great, either. A lot of small voids can be made out, that are exact imprints of grains. Last but not least, there are other, hard, abrasive grains that are nearly 10 times larger than the rated grit of the stone:

SEM micrograph with size measurements of different abrasive grains. Instrument: Zeiss GeminiSEM 560.

We’ll check out the chemical composition in a moment, but already I can tell you – the surface morphology will be dominated by these roughly 10 µm sized particles.

EDS analysis of the Jende 1 µm resin stone. Instrument: Oxford Ultim Max  ∞ 40mm² EDS sensor. Note that our EDS sensor doesn’t show elements lighter than boron.

EDS analysis confirms that these grains are oxide based ceramic abrasive grains. This is bad in multiple ways: first, it will leave scratches in the actual steel matrix of whatever you are sharpening. These grains are hard enough to easily scratch even the hardest martensite. At the same time, their hardness is insufficient to properly cut through most carbides – they dull very quickly, and then create a lot of pressure on the apex. Cracking near the carbides and general smearing around them is the consequence.

EDS overview of the Jende 1 µm resin stone. Note the dominance of larger, oxide abrasive particles. Instrument: Oxford Ultim Max  ∞ 40mm² EDS sensor.

In a larger overwiew zoom, this looks more like a ceramic-resin stone, and less like a diamond stone. Oxide particles dominate!

In order to evaluate the sharpening performance and material removal mode of this stone, a blade was sharpened with it. I am using a standardised testing procedure, read about it here. Nevertheless, it’s 65 HRC M398, and sharpened to 17 DPS with resin bond diamond stones down to 10 µm. Afterwards, the tested stone is used, first in a back and forth movement until the surface becomes homogenous, and then alternating, edge trailing strokes (5-5-3-2) on each side, for a total of 20 strokes towards the apex per side. No pressure is applied but the weight of the apparatus. Moreover, the same approach is repeated with a blade in NitroV at 59-60 HRC.

The edge is then analysed in the electron microscope for breakouts and morphological appearance.

Let’s start with the harder steel – the M398 blade:

SEM micrographs of the M398 edge finished with the Jende 1 µm resin stone. Instrument: Zeiss GeminiSEM 560

Zoomed out, the edge looks quite refined, and the apex itself is pretty sharp as well. Zooming in further, one can see a lot of scratches, a certain raggedness but also clear signs of prow and burr formation, due to the larger particles found in the stone. The optical micrograph further confirms this – this is quite frankly a miserable result for what is supposed to be a 1 µm stone:

Optical micrograph of the M398 bevel. Instrument: Marvscope

Which is further visible in the white light interferometer measurements of the bevel: a diffuse, marred surface:

3D surface height map of the M398 Bevel. Instrument: Zygo NewView 9000, Objective Lens: 20X. Metrological filter chain: LS-Plane to orient data, cutoff 0.1/99.9 percent to remove outliers.

With the surface roughness parameters as follows:

Sa	0.0241	µm
Sq	0.0387	µm
Ssk	-0.5204	–
Sku	12.73	–

ISO 25178 surface roughness parameters. S-Filter: 2.5 µm (gaussian), L Filter: 0.25 mm (gaussian). No F operation besides LSQ leveling.

Let’s take a look at the NitroV edge:

SEM micrographs of the NitroV edge. Instrument: Zeiss GeminiSEM 560

The issues seen in M398 are apparent here as well, with deeper scratches. Compared to the M398, NitroV has much more of the softer steel matrix, so the oxide particles are able to plough and cut deeper into the bevel:

Optical micrograph of the NitroV bevel. Instrument: Marvscope

This is further reflected in the 3D height map:

3D surface height map of the NitroV Bevel. Instrument: Zygo NewView 9000, Objective Lens: 20X. Metrological filter chain: LS-Plane to orient data, cutoff 0.1/99.9 percent to remove outliers.

And a significantly rougher set of surface parameters:

Sa	0.0424	µm
Sq	0.0579	µm
Ssk	-0.2916	–
Sku	4.433	–

ISO 25178 surface roughness parameters. S-Filter: 2.5 µm (gaussian), L Filter: 0.25 mm (gaussian). No F operation besides LSQ leveling.

Not a lot more needs to be said about this stone, so let me sum it up with a bit of a subjective view on it:

The stone itself is quite “quick” in it’s effect. The feedback is similar to other Jende resin stones, as I’d say the mix of resin and filler abrasive particles is dominating. Jende needs to work on mixing, get finer abrasive fillers or skip them completely. A very challenging task for them would be to fix grain adhesion – which might just not be needed at this grain, as a rolling 1 µm stone would quite likely quickly polish any bevel.

I was told beforehand that the 1 µm stone isn’t very good -and my test kind of confirms this. I heard the 3 µm is much better. Overall, the finish of this stone is not at all related to it’s rating, and I think there are a lot of 5 to 3 µm rated stones on the market that can easily outperform this one.

Jende has reached out after my first review, and took my reviews in the best possible way: free, high quality analysis of their stones and the possibility to maybe improve on their product. Kudos to them! I hope they take a look at this as well, and improve on the 1 µm stone. After all, the 120 µm shows there is potential to their abrasive technology.