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!