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 another benchstone – yes, dear readers, we’ve fast arrived at my “benchstone era”. It’s a Shapton glass in the #1000 grit. It’s a japanese aluminium oxide stone with a remarkable reputation.

Optical micrographs of the stone. Instrument: Leica Emspira

The stone itself is an off-white colour, very homogeneous. Touching it feels like touching a slightly gritty ceramic tile – after all, that’s pretty much what it is! Let’s take a look under the scanning electron microscope:

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

I always find it fascinating how the SEM manages to resolve what looks like a very homogeneous, flat stone under the optical microscope into distinct shapes. The stone here shows a flakey, crumbling matrix with lots of slightly flat, cubic abrasive grits in it. This probably is the defining characteristic of the grit rating in ceramic sharpening stones!

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

The stone shows a nice, dense distribution of Al2O3 particles in a MgO matrix. Moreover, some larger SiO2 particles can be made out. I would guess that these wear out first, allowing for some porosity / dimples in the surface where swarf and lubricant can fit in.

In order to evaluate the sharpening performance and material removal mode of this stone, a blade was sharpened with it. As this is a benchstone, I’m using a Katocut Nowi Pro to sharpen the blade and an exact angle and remove the human error. Two blades are sharpened – one is a custom heat treated M398 (65 HRC), one is a commercially available Nitro-V Blade (60 HRC), which shows the stones behaviour in two wonderful steels near the opposite ends of the spectrum of knife steels. The stone was used wet and regularly splashed with water.

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

SEM micrographs of the M398 edge finished with the stone. Instrument: Thermo Fischer PhenomXL SEM.

The stone struggled quite a bit with the M398 edge. Instead of a clean cutting action, one could feel that it is slightly glitching over the surface of the stone, and the edge actually got a bit duller during use, compared to the edge preparation beforehand. In the SEM, we can see that the apex was pushed over – a clear sign that not enough cutting action, but instead a lot of plastic deformation is happening.

Now, in the NitroV steel, this looks completely different:

SEM micrographs of the NitroV edge finished with the stone. Instrument: Thermo Fischer PhenomXL SEM.

The edge is smooth, regular, no plastic deformation. A nice, toothy appearance is visible along the apex. The blade turned out quite sharp, with the surface much more homogeneous than in the M398.

The stone itself is wonderful- the feedback is constant, it is quick cutting in NitroV, and exceptional fun to use, especially as it is splash and go. A well made, affordable gem for sharpening, if your preferred knife steels are not super hard and high carbide content. The results speak for themselves!

I’m really surprised – but have to state that I absolutely love this stone and will use it regularly on my simpler kitchen knifes.

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. The stone for this review was supplied for the manufacturer free of charge. The manufacturer had no influence on this review and did not see it before publication.

Review

Today’s sharpening stone is the finer side of the Cheefarcut Vitrified stone from this series last instalment. While they start to appear as individual stones on the market, this is from a double sided stone, so their “home” series.

Let’s take a look under the microscope!

Optical micrographs of the stone. Instrument: Leica Emspira

The stone looks smooth, regular and slightly porous under the optical microscope. Some darker particles can be made out – especially after seeing the previous stone, I suspect a small amount of filler particles here.

SEM micrographs of the Cheefarcut #1000 stone. Instrument: Zeiss GeminiSEM 560.

I find this again very fascinating. Vitrified stones we’ve had so far in the blog usually had a very dense matrix, but just like the #400 grit, this one is very porous. I’d even go so far as to say it’s not fully “vitrified”, meaning the degree of glassification is not very high. We can make out numerous grains here, but not all of them look like they are diamond. Inter-grain connection is very low and thin. Diamond typically is a wonderful heat conductor – having two separate grain sizes, with different thermal transfer rates show exactly the same level of vitrification makes me believe that it is actually by design and not poor sintering that the stone is so lowly interconnected. It makes the stone more chalky, creating a slushy abrasive mixture while sharpening. This will of course appeal to the “natural stone” fraction!

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

The cheimcal composition checks out to what one would expect from a vitrified stone – lots of oxides in the Mg / Al / Si group, but also larger amounts of oxides with a lower melting point such as Na. We can also detect a non-trace amount of fluoride – not sure why! I would guess it reduces the sintering temperature further? One probably shouldn’t use the abrasive as a toothpaste replacement though! 🙂 Compared to the #400 grit, we can see that the mixing is more difficult, and the distribution along the stone is not as homogeneous. Nevertheless, it really is a high concentration and it contains a lot of diamond!

In order to evaluate the sharpening performance and material removal mode of this stone, a blade was sharpened with it. As this is a benchstone, I’m using a Katocut Nowi Pro to sharpen the blade and an exact angle and remove the human error. Two blades are sharpened – one is a custom heat treated M398 (65 HRC), one is a commercially available Nitro-V Blade (60 HRC), which shows the stones behaviour in two wonderful steels near the opposite ends of the spectrum of knife steels.

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

Let’s start with the M398:

SEM micrographs of the M398 edge finished with the stone. Instrument: Thermo Fischer PhenomXL SEM.

We can see a smoother bevel, but also slightly refined apex compared to the #400 stone. The surface once again shows very few streaks from a grinding action, but again a lot of miniature burrs, prows and other surface defects, likely caused by the rolling grain. Moreover, we can once again make out small black dots – which show in stark contrast on a BSD picture, making them once again embedded diamond particles:

BSD view of the edge sharpened with the Cheefarcut #1000 vitrified diamond. Black spots signify a much lighter element than the surrounding matrix of steel. Instrument: Thermo Fischer PhenomXL.

The edge itself is refined, compared to the #400 grit. There’s still a large-ish amount of burr that gets folded over – I would imagine with some better cutting action, and less rolling grain, this would be a better edge.

Let’s continue with the NitroV:

SEM micrographs of the NitroV edge finished with the stone. Instrument: Thermo Fischer PhenomXL SEM.

Similar results in NitroV – with this amount of diamond, the stone doesn’t really care about the hardness of the steel. The apex is slightly less well defined – with larger pieces of burr just barely hanging on. Overall, this is not a very impressive apex or bevel finish for a #1000 grit stone – pretty much any electroplated stone would leave a better finish, and finer apex. Then again, EP stones will wear quickly – and this one is very thick and will last a lot of blades.

The stone itself was a bit more pleasant to use – it has a chalky, high feedback feel, is solid enough that one doesn’t have to fear about slicing into it – but is also not “stuttering” like the #400 grit did for me. It soaks up quite a bit of water, and I found myself wetting it quite a lot during the sharpening action. With the very porous composition, it has a low of surface area for water to evaporate.

So, would I recommend this stone? Definitely not. While the 400 excels with quick material removal, and with the weakness of the embedding diamonds STILL has a long lifetime for a super low price going for it, at #1000 grit, you are starting to really set your apex for ultimate performance. The pictures above show that this stone is putting a lot of pressure on your blade, the surface finish is mediocre and the apex not super thin. Pretty much any #1000 grit stone reviewed in this blog would leave you with a better edge. Nevertheless, it’s interesting to see that some choices here seem to be by design, and cheefarcut as a company are pleasant to talk to, listening a lot to their customers feedback and seem to iterate quickly. While I don’t like this stone, I will be watching very closely what they come up with and am excited to test new products they come out with!

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. The stone for this review was supplied for the manufacturer free of charge. The manufacturer had no influence on this review and did not see it before publication.

Review

Today’s sharpening stone is a vitrified one with “a very high diamond concentration“. It’s the Cheefarcut Vitrified “Home” stone, which comes in 400 and 1000 grit size (a double sided one), and this review is about the coarser 400 grit side.

Let’s take a look under the optical microscope!

Optical micrographs of the Cheefarcut 400 vitrified diamond stone. Instrument: Leica Emspira

The stone is a nice, green colour. The large diamonds are easily made out – but there’s a lot of grains in there, and not all of them sparkle! Let’s take a closer look under the SEM:

SEM micrographs of the Cheefarcut 400 vitrified diamond stone. Instrument: Zeiss GeminiSEM 560.

I find this very fascinating. Vitrified stones we’ve had so far in the blog usually had a very dense matrix, whereas this one is very porous. I’d even go so far as to say it’s not fully “vitrified”, meaning the degree of glassification is not very high. We can make out numerous grains here, but not all of them look like they are diamond. Inter-grain connection is very low and thin.

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 Cheefarcut 400 vitrified diamond stone. Instrument: Oxford Ultim Max  ∞ 40mm² EDS sensor. Note that our EDS sensor doesn’t show elements lighter than boron.

We can make out that this is a typical vitrified bond, with large amounts of Mg, Al, Si and Na in it. The diamond concentration is highlighted by the carbon channel, and we can see that there’s a really decent concentration of diamonds in the stone, albeit particle size control does not look very good and there’s a slight tendency for agglomeration. This becomes more visible when zooming out to a larger FOV:

EDS analysis of the Cheefarcut 400 vitrified diamond stone. Instrument: Oxford Ultim Max  ∞ 40mm² EDS sensor. Note that our EDS sensor doesn’t show elements lighter than boron.

In order to evaluate the sharpening performance and material removal mode of this stone, a blade was sharpened with it. As this is a benchstone, I’m using a Katocut Nowi Pro to sharpen the blade and an exact angle and remove the human error. Two blades are sharpened – one is a custom heat treated M398 (65 HRC), one is a commercially available Nitro-V Blade (60 HRC), which shows the stones behaviour in two wonderful steels near the opposite ends of the spectrum of knife steels.

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

The stone itself is curious to use. On the first stroke, it feels very much like a ceramic stone – there’s a lot of friction, which often gets labeled as feedback. Something I found curious is that on some movements, the stone feels a bit like rubber, and the blade starts vibrating and making noises, similar to a piece of chalk starting to jump over a whiteboard, just at a low frequency.

Obviously, I used very little pressure, but as it is a coarse stone, some pressure is applied. During the sharpening action, a lot of debris builds up on the stone – some of it is clearly identifiable as material from the stone, some is the swarf from our blade. Compared to other vitrified stones, this feels much more like chalk, and less like a fully sintered/bound bond.

Let’s take a look at the blade in M398:

SEM micrographs of the M398 (65 HRC) edge finished with the stone. Instrument: Thermo Fischer PhenomXL SEM.

The SEM pictures show a nicely formed apex for such a coarse stone. The edge is very toothy, but at that grain size this is expected behaviour. What I find very curious is that the surface is marred with a lot of structures. Most of these can be contributed to plastic deformation – such as burrs, prows and even some voids. I would guess that this stems from free, rolling grains.

The optical micrographs show a rough surface on the bevel, where the defects are clearly visible as matte structures:

Optical micrographs of the M398 (65 HRC) edge finished with the stone. Instrument: Leica Emspira.

Next, let’s take a look at the Nitro-V blade! It felt pretty much the same while sharpening, but a quicker material removal / swarf build up was noticeable.

SEM micrographs of the Nitro-V (60 HRC) edge finished with the stone. Instrument: Thermo Fischer PhenomXL SEM.

In the SEM, a large folded over portion is visible. It is a bit thicker than what I would call a burr – this is once again something that feels very much like a burr to your finger, but is actually plastic deformation of the whole cutting edge, and not yet the sign of a formed apex.

Optical micrographs of the M398 (65 HRC) edge finished with the stone. Instrument: Leica Emspira.

This is also visible under the optical microscope. The surface finish of this blade is much better though – a curious result!

The bad surface finish in M398 made me turn on the BSD sensor of the SEM. This specific sensor detects not so much the topograhpy of a sample, but instead gives us “elemental contrast”. here, the brighter regions are heavier elements, whereas darker areas are lighter elements. Surprisingly, a large number of dark particles embedded themselves into the blade material!

SEM Micrographs with the BSD detector (showing elemental contrast), highlighting small diamond particles that embedded themselves into the blade near the apex. Instrument: Thermo Fischer PhenomXL

EDS analysis shows these particles to be carbon, so most likely diamond:

EDS linescan over one of the embedded particles. Instrument: Thermo Fischer PhenomXL.

This is quite fascinating to me. The stone, as mentioned before has the tendency to develop a little bit of a slurry, very similar to a natural stone. I’ve not yet sharpened a blade on a slurry of diamonds – but this is a very fitting explanation for the structures we see on the blade. The rolling diamond is creating the large prows and plastic formations visible on the surface – it’s no longer a “grinding” tool by it’s technical definition (path constrained abrasive), but turns into a lapping (only force constrained abrasive) stone – or a mix in between.

Overall, this was an interesting and novel approach to a vitrified stone. It’s by far the cheapest vitrified stone on the market, and it contains a large amount of diamonds. The result is very unlike what is shown on the manufacturers homepage – there’s not really a fine burr formed, but instead the whole bevel pushed over. Furthermore, the stone, while pretty thick itself, wears itself down to form the slurry. This is something I’m not used to on ceramic or vitrified stones – they typically don’t show any apparent wear. Just like with everything, there’s an upside to this: the stone constantly self sharpens, and there’s no time for debris to get struck. Just rinse under running water and it becomes pretty clean again.

Would I recommend this stone? Probably not. The manufacturing looks to me like it is of insufficient quality – mixing, sintering and overall composition sure are points that could and should be improved. Then again, it’s a very cheap stone for what it is – thick, lots of diamonds and the start of what could be called a vitrified bond.

Especially the embedding diamonds will make subsequent sharpening actions more difficult, and the surface finish left is abysmal compared to the material removal rate. I think going for an ATOMA F400 is the better choice if you are chasing perfection and want a solid foundation for further sharpening. Nevertheless, I will be watching (and testing!) very closely what this new Cheefarcut company comes up with.