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. The stones in this review were bartered for – a set of mine vs a set of these.

Review

Today’s sharpening stone is something very special. I’m frankly quite giddy as I am writing these lines – gentle readers, I am ecstatic to present you the review on the brandnew “Grain&Bond” – Sol Gel (SG) Sharpening stones – from Likhovtsov Abrasives Lab.

These sharpening stones were launched in the past 24 hours. They are the product of Alexander Likhovtsov, someone I consider a master in abrasives from Russia. The stones reviewed are two different grit sizes, F120 (120 µm) and F220 (63 µm).

Let’s dig into it:

The bright blue “F120” and “F220” SG stone. Do note: The stones being sold have a different laser engraving on the anodised aluminium blank.

The “SG” stands for sol-gel, the production process of the Al2O3 (Corund) abrasive these are based on. To expand, why this is exciting, you have to understand how aluminium oxide as an abrasive is made:

There are basically two methods in producing the popular abrasive. Large scale, one can melt Al2O3 into a large block, cool it down and then crush it into small pieces. These are then sorted by size, which makes for a very economic, hard powder. The individual grains themselves consist of only a few crystals, often micrometre sized.

The second industrial method is to mix precursors together, dry them until they form a gel, and then sinter the mixture before crushing and sorting for size. Here, each individual grain is polycrystalline, consisting out of a large number of often nanometre sized crystallites.

In their behaviour, they differ wildly. The molten Al2O3 dulls, and at some point fractures into large segments. The sol-gel Al2O3 meanwhile constantly exhibits micro fractures, that renew the cutting edge. This gives less of a glassy, dull feel during sharpening, but also a more homogeneous result. The downside to SG-Al2O3 is of course the cost – it costs multiple times more than regular melt-produced Al2O3.

You might ask: how does this translates to visible grain morphology? Don’t worry, I got you covered. Compare the SG grain with a similar sized molten Al2O3 grain, in the same binder:

Comparison in grain morphology between F220 sized grains – left/first picture is the SG-Al2O3, second/right picture is the molten AL2O3.

You can see that the SG-Al2O3 has a much smoother, flatter, and less ragged appearance. The molten Al2O3 initially shows a lot of ragged cutting edges from the crushing of the grain, but is also much more blocky – this is an increase in engagement volume, which makes cutting of hard steels more difficult, and typically quicker leads to a dull, burnishing feeling.

Let’s take a look under the optical microscope!

Optical micrographs of the Grain & Bond SG F120 (first/left picture) and SG F220 (second/right picture) stone. Instrument: Marvscope

The bright blue colour comes through very nicely in the optical microscope images. On the F120 size, we can make out the individual grains very easily. The are elongated, smooth and flat ones. The finer F220 stone meanwhile shows a few more white grains, as well as smaller, more blocky and square abrasive grains.

Let’s take a closer look in the SEM, first for the SG F120:

SEM micrographs of the Grain & Bond SG F120 stone. Instrument: Zeiss GeminiSEM 560.

The stones shows a large number of grains. They are a mix of flat, elongated grains and some blocky ones with multiple, ragged cutting edges visible. The overall concentration is quite high. Between the grains, we can see a grumbly, very small and dense binder. Some controlled and evenly distributed porosity is visible in the stone, which is a good sign on such a large grit – this gives some space for lubrication and swarf!

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 Grain & Bond SG F120 stone. Instrument: Oxford Ultim Max  ∞ 40mm² EDS sensor. Note that our EDS sensor doesn’t show elements lighter than boron.

The EDS analysis shows a large concentration of AO as abrasive in this stone, with some minor, very small SiC distributed on the surface – I would guess, probably from the manufacturing process. The binder mostly shows carbon – which to me makes this a resin stone? It has a surprising hardness, more on this later.

Next, let us take a closer look at the F220 stone:

SEM micrographs of the Grain & Bond SG F220 stone. Instrument: Zeiss GeminiSEM 560.

The finer stone shows a high conecntration of grains. They are a bit flatter, and oriented in a random way across the surface. Size is spot on, and it has a very homogeneous distribution.

Let’s take a quick look at the EDS:

EDS analysis of the Grain & Bond SG F220 stone. Instrument: Oxford Ultim Max  ∞ 40mm² EDS sensor. Note that our EDS sensor doesn’t show elements lighter than boron.

A bit more trace particles – we can find some magnesium, some sodium and some more silicon. Not quite as pure as the F120 stone, but at the same time: they are in a size where the AO abrasive still dominates the result.

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.

First, let’s take a look at the F120 (120 µm) SG stone:

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

SEM micrographs of the M398 edge finished with the Grain & Bond SG F120 stone. Instrument: Zeiss GeminiSEM 560

Most AO and natural stones struggle a lot with the M398 I use for my reviews. While sharpening the blade for the analytics, I was quite surprised by the amount of black swarf that was created – but also by the delicate, fine apex. Typically, on non-superabrasive stones, these blades maybe get burnished, but the apex is dulled and rounded over. The SG can’t compete with diamond in this steel – but it leaves all other AO stones I’ve had on this blog far, far behind. I’d say the result is even better than comparable sized chinese OEM diamond resin stones, which is…wild.

THe morphology shows large, burnished sections, but also some clear cutting action near the apex. A couple deeper scratches and a slight waviness, giving a toothy edge can be made out and are of course also reflected in the optical micrograph:

Optical micrograph of the M398 bevel finished with the Grain & Bond SG F120 stone. Instrument: Marvscope

Which is further visible in the white light interferometer measurements of the bevel: a smoothed over surface, with a couple of deeper scratches.

3D surface height map of the M398 Bevel finished with the Grain & Bond SG F120 stone. 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 exceptional for a 120 µm sized stone:

Sa	0.1752	µm
Sq	0.2636	µm
Ssk	-1.605	–
Sku	7.810	–

ISO 25178 surface roughness parameters. S-Filter: 2.5 µm (gaussian), L Filter: 0.08 mm (gaussian). No F operation besides LSQ leveling.

Let’s take a look at the NitroV edge:

SEM micrographs of the NitroV edgefinished with the Grain & Bond SG F120 stone. Instrument: Zeiss GeminiSEM 560

The softer steel is, quite expected, a much better target for the SG stone. We get a very fine apex for this grit size, with a regular appearance and morphology.

Optical micrograph of the NitroV bevel finished with the Grain & Bond SG F120 stone.. Instrument: Marvscope

The optical micrograph shows a super smooth, regular bevel with some toothiness to the cutting edge. It is very pleasing, a matte, regular and homogeneous result!

3D surface height map of the NitroV Bevel finished with the Grain & Bond SG F120 stone.. 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 a bit lower compared to the M398 steel:

Sa	0.1205	µm
Sq	0.1649	µm
Ssk	-1.209	–
Sku	5.458	–

ISO 25178 surface roughness parameters. S-Filter: 2.5 µm (gaussian), L Filter: 0.08 mm (gaussian). No F operation besides LSQ leveling.

Next, we’re going to look at the results of the F220 (63 µm) SG stone:

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

SEM micrographs of the M398 edge finished with the Grain & Bond SG F220 stone. Instrument: Zeiss GeminiSEM 560

The stone improved the surface finish noticeably. The bevel still has some deeper scratches, but overall it is very smooth already.

Optical micrograph of the M398 bevel finished with the Grain & Bond SG F220 stone. Instrument: Marvscope

The optical micrograph shows this in the form of very little contrast – besides the deeper scratches.

3D surface height map of the M398 Bevel finished with the Grain & Bond SG F220 stone. Instrument: Zygo NewView 9000, Objective Lens: 20X. Metrological filter chain: LS-Plane to orient data, cutoff 0.1/99.9 percent to remove outliers.

Which also is reflected in improved surface parameters:

Sa	0.1498	µm
Sq	0.2226	µm
Ssk	-1.34	–
Sku	7.385	–

ISO 25178 surface roughness parameters. S-Filter: 2.5 µm (gaussian), L Filter: 0.08 mm (gaussian). No F operation besides LSQ leveling.

Let’s take a look at the NitroV edge:

SEM micrographs of the NitroV edge finished with the Grain & Bond SG F220 stone. Instrument: Zeiss GeminiSEM 560

The difference is not quite as stark as it is with the M398 steel, but some refinement can be made out. Moreover, a higher amount of cutting traces instead of burnishing can identified. The apex is further refined – this was already quite the sharp knife!

Optical micrograph of the NitroV bevel finished with the Grain & Bond SG F220 stone. Instrument: Marvscope

The optical appearance of the bevel is a lovely, matte and diffuse, very regular scratch pattern – also exceptionally regular under the WLI:

3D surface height map of the NitroV Bevel finished with the Grain & Bond SG F220 stone. 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 quite low surface roughness parameters – keep in mind this is a 63 µm sized stone!

Sa	0.1170	µm
Sq	0.1574	µm
Ssk	-1.113	–
Sku	5.905	–

ISO 25178 surface roughness parameters. S-Filter: 2.5 µm (gaussian), L Filter: 0.08 mm (gaussian). No F operation besides LSQ leveling.

The stone itself has a high & wonderful feedback. I’m very much reminded of a Shapton Glass, which (up until this stone!) has been a favourite of mine. The stone pics up speed after a couple of strokes, with some slush being created and accelerating the sharpening action. From time to time, a larger grain comes loose – this can be felt and probably explains the deeper scratches. I found that during the couple of hours I spend with this stone, that the speed stayed identical. The typical glazing over that AO stones experience did not happen on this.

I would classify the binder as resin, based on the chemical composition visible in the EDS, even though it is unbelievably hard. I think this is probably the hardest resin stone I ever had on the blog – and this just screams at the manufacturer that there should be a benchstone coming soon, for the freehanders.

The results speak for themselves – a surface finish, factors better than I would imagine an Al2O3 stone could produce. Still working in what is widely considered a difficult super steel. Sharp edges. Wonderful feedback. Good lifetime. Available in 1×6″ format. Affordable price.This stone, to me personally is the “Shapton killer”.

There is very little that could be improved – and so I can only advise you to buy these, with no idea how you would get about doing this outside Russia. Let’s hope they arrive on our markets soon!

I can only end this review by taking my hat off to Alexander Likhovtsov – Моё почтение! Шедевр!

What a wonderful stone. I love it.

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 the KDTU Silver CBN. According to the shop where I bought it, it features an “advanced hybrid bond enriched with tin and silver-based components, this stone features a distinctive silver-colored abrasive surface — the defining characteristic of the KDTU Silver Stones Series“

Alright. Sounds good. One thing that immediately stands out to me is the very dark colour of the stone. In a previous review, I quoted the manufacturer who said that discolouration is just something inherent to the stones, but the review proofed that it was a sign of bad mixing. I have high hopes that this stone is now better mixed, and not just coloured black to hide mediocre manufacturing.

Let’s take a look under the optical microscope!

Optical micrographs of the stone. Instrument: Marvscope

The stone shows a dark, grey/silver bond. We can immediately make out black CBN grains, which tend to cluster together. Moreover, there’s some streaks of a bronze coloured material visible as well. Honestly: looks pretty cool!

Let’s take a closer look in the SEM:

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

The SEM pictures show a fine, very dense bond. The abrasive particles are held tightly inside this bond. They are of a very square and blocky type.

The bond is surprisingly dense for a metal bond – most bronze bonds are a bit looser.

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.

In the EDS analysis, the dense bond is explained – it consists mainly out of aluminium, with some copper, tin, and zinc. The before-mentioned silver that gives this stone it’s name can also be found – in a sub 1% concentration. Silver often is used as either a flux or wetting agent to enhance grain retention. Moreover, we can find some silicon (Carbide?) particles, which are smaller than the CBN. Zooming out, one can see a decent amount of CBN, with an overall mediocre distribution. There’s some clustering, but at this stones grit this will not be a major issue.

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 stone. Instrument: Zeiss GeminiSEM 560

The stone left a smooth bevel finish. We can see major signs of ploughing and burnishing – every track of the abrasive grain shows microburr and prow formation at the side. This is a clear sign of plastic deformation instead of clean cutting action. Zooming in to higher magnifications, we can see that the stone created enough pressure that pieces of the steel broke away or fractured near the apex. Nevertheless, the finish is very homogeneous and quite smooth for such a coarse stone.

This is confirmed in the optical micrograph, showing a very matte, silvery and homogeneous finish (do ignore the water drop stains on it – mea culpa maxima!)

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	0.3957	µm
Sq	0.5222	µm
Ssk	-0.608	–
Sku	4.854	–

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

Overall, this is a decent result in terms of surface finish and bevel appearance, but has not really refined the apex massively.

Let’s take a look at the NitroV edge:

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

The softer steel shows less cracking and damage near the apex, but we can also make out large, plastic deformed regions – some part of it has just bend over. Moreover, the surface morphology is once again showing the typical plastic deformation associated with burnishing.

Optical micrograph of the NitroV bevel. Instrument: Marvscope

The edge of the blade is quite ragged, even for this grit of finishing.

In the WLI measurement some deeper scratches can be made out:

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.

With a slightly higher surface roughness on this bevel:

Sa	0.4340	µm
Sq	0.5652	µm
Ssk	-0.2213	–
Sku	3.939	–

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 is pleasant to use. It has a smooth, high feedback feel to it, and is very aggressive in the beginning. After some sharpening action, it loads and becomes a bit slower, but during my test not massively so. It cleans up with a bit of vigorous rubbing.

If I compare the results with the previous coarse CBN stone review from KDTU, I’d say it’s a small improvement, only detectable under advanced microscopes. Mixing still seems to be an area where KDTU struggles, like most abrasive manufacturers. To me, it feels like the harder bond is much tougher on the apex, but the overall feel in sharpening on this one has improved, as did the surface finish.

This brings me to my biggest issue with this stone & manufacturer:

The Ukranian manufacturers (PDT and KDTU) seem to be huge fans of CBN, which is only understandable seeing that during the soviet era, they were a major producer of CBN and still publish a lot of research on it via the V. Bakul Institute for Superhard Materials, a Ukrainian state founded research center for superabrasives. This is reflected in their marketing campaigns pushing these stones. Moreover, their product strategy seems to be the constant release of slightly improved abrasives, since I’ve had this stone 2 more lines came out. This is fine, but for me as a paying customer, it feels like I constantly need to open my wallet to get the latest and newest -and they all fall short of the competition, with no huge improvements.

There is a plethora of stones that outperform this one – both with aluminium oxide or diamond as an abrasive. While this stone is pleasant to use, I’d say there are better choices available.

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

I’m always hesitant to review Chinese sharpening stones. I feel like any review is only a snapshot of a moment, a fleeting statement: this was the one I bought, no idea what the next batch will look like, as they are constantly changing, evolving, backtracking in their recipes. The company who made today’s sharpening stone even reached out, offering me a collaboration. I politely refused, and instead ordered this stone with my own money. Let’s dig into Forever Superabrasives Resin bonded diamond Stone – 400/1000 grit. I’ll split the important picture galleries in two parts, some might combine the sides. Please refer to the caption to see which is which.

Let’s take a look under the optical microscope!

Optical micrographs of the (left/first/green) 400 side and the (right/second/red) 1000 grit side of the Forever Superabrasives Resin bonded diamond stone. Instrument: Marvscope

The stone is probably coloured, as the difference between the two sides is quite stark. The coarser, #400 grit side shows an overall green appearance, with some copper coloured agglomerates. The finer, #1000 grit side is more homogeneous coloured, but has large, white-grey particles or agglomerates.

Let’s take a closer look at the #400 side in the SEM:

SEM micrographs of the #400 stone. Instrument: Zeiss GeminiSEM 560.

We can see a plethora of different particles here. The bond itself looks like a phenolic resin bond, based on it’s grumbly appearance. A large amount of small particles is interspersed. We can also make out some voids that look like the contour of bubbles. Grain adhesion doesn’t seem to be super high, as most of the larger grains are already showing some separation from the bond.

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 EDS analysis shows a medium diamond concentration. The large, copper coloured particles seen in the optical micrograph are actually Copper and Zinc – with quite a bit more Zinc than copper. There is also quite a bit of chromium oxide, correlating to the fine particles, but also the green colour of this side. Lastly, the usual SiC that creates the haptic feedback can be found. Overall, mixing looks like it could be improved – while the diamond is distributed quite nicely, as is expected of this particle size – the other components of this bond seem to agglomerate, and break up the regular diamond distribution. Moreover, I do not see why a manual bond would require any metal components – those are typically added for heat conductivity, and there’s not a lot of heat generated at manual speeds.

Let’s take a closer look at the #1000 side in the SEM:

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

It seems to me like this is a very similar bond- but struggling more from larger agglomerates of fine filler particles. This side also looks to me like it got baked warmer – the phenolic is less crumbly and more solid.

Let’s check out the #1000 grit side’s EDS:

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 visual impression from the SEM pictures is confirmed in the SEM. Most of the components from the #400 grit side can be found, but also large amounts of Iron as well as a much higher concentration of sodium. I would guess that the sodium (Na) is maybe some pressing agent, that did not fully debind during initial baking? Very curious. Mixing is a bit worse, which was to be expected – smaller particles are harder to distribute.

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.  As this is a benchstone, I use a Katocut Nowi Pro to keep the angle constant and get comparable results without much of a human error.

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

First, let’s dig through the 400 grit side – and we’ll start with the harder steel – the M398 blade:

SEM micrographs of the M398 edge finished with the 400 stone. Instrument: Zeiss GeminiSEM 560

Two things stand out immediately to me: Quite a lot of burr, bend over, but also a remarkably smooth bevel at this grit size. The scratch pattern is pretty reglular, with some deeper scratches. The apex is still quite wide – this definitely is the stone to remove material, and not finish a blade. It doesn’t look like the stone is really freely cutting, instead there’s a lot of burnishing, which of course helps with the surface roughness.

Optical micrograph of the M398 bevel. Instrument: Marvscope

The WLI measurement confirms the large burr, and regular scratch pattern:

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	0.1211	µm
Sq	0.1552	µm
Ssk	-0.4174	–
Sku	3.965	–

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 softer steel is less polished, and the apex quite a bit finer. The stone cuts more easily into it.

Optical micrograph of the NitroV bevel. Instrument: Marvscope

This is reflected in a more irregular surface in the WLI measurements:

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.

Which result in a higher surface roughness:

Sa	0.2022	µm
Sq	0.2674	µm
Ssk	-0.4928	–
Sku	4.637	–

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

Now, let’s see how the #1000 grit side performs!

SEM micrographs of the M398 edge finished with the #1000 stone. Instrument: Zeiss GeminiSEM 560

The large burr formation, even folding over the burr completely, in combination with the surface morphology that shows a lot off miniature burr and prow formation shows that the stone struggles a lot with cutting into the hard M398. It is of course removing material, but also damaging the apex and matrix of the steel here due to the plastic deformation.

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 improved quite a bit compared to the #400 grit side:

Sa	0.0946	µm
Sq	0.1212	µm
Ssk	-0.2354	–
Sku	3.518	–

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 #1000 grit seems to be a quite a bit cleaner in this softer steel. The finish on the bevel is matte, with some irregular streaks caused by rolling grains.

Optical micrograph of the NitroV bevel. Instrument: Marvscope

Overall, the stone has typical , high filler particle resin bond feedback. There’s a certain vibration, firmness that makes it easy to keep a good angle when freehanding. It’s speed is average, the composition and manufacturing could be improved.

The results are okay. We recently had the #1000 grit Edgeworks DMT Resin stone in this blog – all objective parameters point to that one being ever so slightly better, but not decisive.

Price wise, it’s hard to beat this stone – you get diamonds, a decent feedback, in a very affordable (around 120€/$ at the time of this review) package that consists of actually two stones. This stone does get a knife sharp. It does refine the apex and bevel.

The problem is: performance is okay. Just okay, not superb, and objective measurement shows it doesn’t live up to the hype on the internet, pushed forward by cooperations and affiliate links. This leaves a slightly bitter feeling, and I think you can feel in these last paragraphs how disappointed I am.

If you don’t have powder steels, I’d instead get a Shapton Glass. I find the feedback on that one unbeaten – and the results are exceptional homogeneous. It is a little bit cheaper individually, and made by a wonderful company in Japan – with a proven record of quality & consistency.

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 the finer brother to our last instalment – the Naniwa Diamond Pro 3000 grit.

It is a very pretty stone – an unusual blue colour with a finely bead-blasted aluminium base:

Let’s take a look under the optical microscope!

Optical micrographs of the Naniwa Diamond Pro 3000 stone. Instrument: Marvscope

The stone shows a very irregular appearance in the optical microscope. We can differentiate between (probably) the diamond in green clusters, a blue phase that likely is the coloured binder, some grey-ish phases as well as a couple of very, very red spots. Intriguing!

Let’s take a closer look in the SEM:

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

The stone shows, quite similar to it’s caorser brother, a standard phenolic bond. The grain adhesion seems to be similar. There are some larger particles visible, but also a lot of micron or sub micron particles.

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 EDS reveals what I already suspected in the optical micrograph – mixing in this stone isn’t particularly well. There are large areas, where the friable Na-Al-F compound where I suspect it is the mineral cryolite (sodium hexafluoroaluminate) absolutely dominates. It seems to be much finer than on the 600 grit stone, but the finer powder clumped together and created some hollow voids where the surface is littered with it. Moreover, we can make out quite the agglomeration of diamond – instead of an even spread, multiple nests of diamond can be made out. There is also again a large amount of SiC, but very, very fine.

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. As this is a benchstone, I differ from the usual process by using a Katocut Nowi Pro to keep the angle constant. 2 blades are sharpened, one in 65 HRC M398, one in 59-60 HRC Nitro V.

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 stone. Instrument: Zeiss GeminiSEM 560

The blade shows a much refined apex compared to the 600 grit stone. The bevel has gotten much smoother, we can easily identify the carbides. Nevertheless, we can still a lot of random direction marring of the surface – very likely caused by the rolling grain accumulating on the stone. I would guess that this is by design – it emulates the feeling of natural japanese stones, where a slush of abrasives builds up, and of course speeds up the stone. Nevertheless, it’s not as clean as firmly bound abrasive, which is reflected in the optical images:

Optical micrograph of the M398 bevel. Instrument: Marvscope

The WLI measurement shows a curious wave like structure parallel to the apex – I’d guess that this is caused by the abrasive slurry?

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.

The bevel itself is quite smooth, with the surface roughness parameters as follows:

Sa	0.0471	µm
Sq	0.0635	µm
Ssk	-0.19	–
Sku	4.740	–

ISO 25178 surface roughness parameters. S-Filter: 2.5 µm (gaussian), L Filter: 0.08 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

Again, similar to the 600 grit stone, the surface is slightly less polished, with deeper scratches. The optical micrograph shows a very matte, but uniform appearance with a few random deeper scratches:

Optical micrograph of the NitroV bevel. Instrument: Marvscope

The WLI measurement shows again this very curious double wave-structure close to the apex.

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 parameters have improved, but are a bit worse than on the M398 blade:

Sa	0.0671	µm
Sq	0.0875	µm
Ssk	-0.2729	–
Sku	3.920	–

ISO 25178 surface roughness parameters. S-Filter: 2.5 µm (gaussian), L Filter: 0.08 mm (gaussian). No F operation besides LSQ leveling.

The stone itself still has a surprising amount of feedback for it’s 3000 grit rating. It leaves the bevel with a very matte, diffuse appearance, which is at least to me quite appealing, but a far stretch from a mirror finish. I feel like it is held back by it’s mediocre mixing and the large amount of filler particles. The result is a refinement of the blade, both in surface roughness but also apex width, and I would guess that with some medium duty stropping, one could get a very good edge of this.

Considering that the price of this stone is quite high in my home country of Germany. Unlike the 600 grit, I don’t really like this stone, and I think there are much better alternatives out there.

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

I’ve kind of been avoiding today’s sharpening stone – they are after all quite pricey! But, I am very glad I finally got around to it when they were on sale in Germany. Gentle readers, today we are taking a look at the very well reputed Naniwa Diamond Pro in it’s 600 Grit version!

Let’s take a look under the optical microscope!

Optical micrographs of the Naniwa Diamond Pro 600 stone. Instrument: Marvscope

This is going to be an interesting stone. We can see a mixture of a lot of different colours, but also different particle sizes.

Let’s take a closer look in the SEM:

SEM micrographs of the Naniwa Diamond Pro 600 stone. Instrument: Zeiss GeminiSEM 560.

The stone shows a standard, phenolic, grumbly and quite fine resin bond. The grains do not seem to be embedded very firmly – on the top layer, one can make out gaps between the grains and the resin bond. Moreover, there is a large difference in size of the particles: some small, sub 5 micron particles, but also larger particles around 30 micrometre.

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 Naniwa Diamond Pro 600 resin stone. Instrument: Oxford Ultim Max  ∞ 40mm² EDS sensor. Note that our EDS sensor doesn’t show elements lighter than boron.

As I suspected in the optical micrograph, this stone consists out of several different abrasives. We have the diamond, which shows a medium concentration, but also a slight tendency to clump together. My understanding is that Naniwa uses concrete style mixers, and I have to give them kudos here – I expected much worse. We can see several secondary abrasives (I learned that term from the TSPROF marketing guy to justify their new series parasitic grains, and I am now going to use it to the end of eternity…), mostly SiC which is used as a filler particle (that is the correct term) to increase hardness of the bond, but also some Al-Na-O-F compounds, which is typically the mineral cryolite (sodium hexafluoroaluminate). It helps to reduce loading, but also for the bond to break down and renew the surface. This is one hightech abrasive here, I expected nothing else from Naniwa.

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. As this is a benchstone, I differ from the usual process by using a Katocut Nowi Pro to keep the angle constant. 2 blades are sharpened, one in 65 HRC M398, one in 59-60 HRC Nitro V.

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 Naniwa Diamond Pro 600 resin stone. Instrument: Zeiss GeminiSEM 560

The stone left a slightly marred surface, but for 600 grit this is quite fine. The apex is very straight, albeit not super sharp. I would say for this grit size, this is totally fine and a good result. The bevel itself is slightly marred – one could feel the bond slightly breaking down, and the slush on the surface likely contains a large amount of rolling grains. This is reflected in the optical micrograph, which shows a very matte and diffusely scratched appearance:

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	0.3037	µm
Sq	0.4004	µm
Ssk	-0.7666	–
Sku	4.773	–

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 rolling particles seem to have created a more diffuse and locally pitted surface in the softer steel, whereas at the same time the scratches appear less deep to me.

Optical micrograph of the NitroV bevel. Instrument: Marvscope

Very slight raising of the apex is visible in the WLI images – I would guess that the softer steel is slightly deformed here.

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.

Surface roughness is quite good for such a coarse stone:

Sa	0.2510	µm
Sq	0.3384	µm
Ssk	-1.031	–
Sku	5.741	–

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

Overall, the stone has a pleasant feedback. It is regular, homogeneous and for a resin stone quite hard. The reputation for freehand sharpening is well earned.

The results are totally fine for a 600 grit stone, with good, high-tech composition, decent mixing and abrasive grain density.

I think the only issue one can have with this stone is the (in Germany) quite high price tag for a very thin layer. I heard that they are prone to wearing a bit quicker than other stones, which makes this an expensive stone with a high performance. When you compare it’s performance to a shapton glass for example. I do not think it is justified. Nevertheless, I like it and am absolutely looking forward to trying it’s finer brother soon!

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.

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

In the last part of this series, we took a look at the brand new DiamondMax 80 Grit (160 µm) from Edge Pro. The review turned out to be quite the disappointment – the stone was suffering from heavy grain loss. Now, while it definitely is possible to make a resin stone at that grain size that works nicely, the main application of resin bond sharpening stones is the finishing – this is after all something where they shine. Our next look at this new series is the exact opposite end of the spectrum – the Diamond Max 4000 grit (5 µm). I’ve had a Diamond Matrix stone in a previous review.

I’d advise you to check out my review on the 80 grit first:

A brief study on sharpening stones – Part 62 – Edge Pro Diamond Max 160 µm (Diamond, Resin)

The manufacturer of the stones, David from CGSW has meanwhile commented under that blog post and given a more detailed insight into the increased diamond ratios. As this is very interesting, I’d like to quote him here:

“To be clear, all Matrix stones have had more than 50% diamond to resin content by weight in them, and I have made every single one of them, so I can say this with confidence. The 80 grit Max stone has a 2.5 times higher concentration of diamonds, the 250 2.2 times higher, the 450 through 1700 have 2 times higher, and the 4000 1.8 times higher concentration of diamonds. For perspective, if they started out at 50/50, then 67/33 is double the concentration. I put the maximum amount of diamonds in the Max stones as is feasible for this resin. If I put more diamonds in this resin I run into processing problems.” – David from CGSW, commenting on my blog (Part 62) on the 24th of May 2026

This is clarifying a point, as it doesn’t mean these contain twice the amount of diamond, it just means the ratio has shifted – 67% by weight is after all just 35% more diamond.

The original Diamond Matrix in 5 µm size is one of the stones I consider very, very good. My major issues back then was the slow speed – let’s take a look at the new DiamondMax in 5 µm!

As always, we will start under the optical microscope:

Optical micrographs of the Edge Pro Diamond Max 5 µm stone. Instrument: Marvscope

The stone has a very homogeneous, regular appearance. The diamond can barely be made out at this magnification – just like I would expect of a 5 micron stone!

Let’s take a closer look in the SEM:

SEM micrographs of the Edge Pro Diamond Max 5 µm stone. Instrument: Zeiss GeminiSEM 560.

We can see that this really is a high concentration stone! there’s diamond just about everywhere on the stone. No foreign particles jump out immediately. Unfortunately, just like with the 160 µm stone, some voids can be seen, and the remaining particles don’t show perfect, solid embedding either.

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 Edge Pro Diamond Max 5 µm stone. Instrument: Oxford Ultim Max  ∞ 40mm² EDS sensor. Note that our EDS sensor doesn’t show elements lighter than boron.

The EDS definitely confirms the view – this is a LOADED stone. Lot’s of diamond. The distribution is good, but not perfect. Some foreign particles can be made out – those are ceramic particles from the manufacturers dressing.

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 Edge Pro Diamond Max 5 µm stone. Instrument: Zeiss GeminiSEM 560

We get a good result here. The bevel is polished, shiny and the carbides are easily identified – typically a sure sign for higher polishing abilities! The apex is smooth, with very little damages visible. At higher magnifications (1kx, 5kx), once can see some scratches that very likely are from rolling, free grain. These are characterised by their appearance in the middle of the bevel – whereas embedded particles in the stone typically show up as scratches that go along the full length of the stone.

Optical micrograph of the M398 bevel. Instrument: Marvscope

Let us take a look at the surface height map:

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	0.00713	µm
Sq	0.009512	µm
Ssk	-0.8962	–
Sku	5.805	–

ISO 25178 surface roughness parameters. S-Filter: 2.5 µm (gaussian), L Filter: 0.08 mm (gaussian). No F operation besides LSQ leveling.

This is a very respectable result! A nanometric surface roughness, especially in the single digit range is a finely polished, mirror like surface.

Let’s take a look at the NitroV edge:

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

The DiamondMax had a bit more issues on this steel – something that is often seen on soft diamond stones when used on softer, less high tech steels. Nevertheless, we get a fine apex, and a relatively smooth surface. Near the apex, more damage from rolling grain can be seen. The bevel on this test blade is a bit wider than on my M398, I’d guess that this allowed for more swarf to buildup.

Optical micrograph of the NitroV bevel. Instrument: Marvscope

Overall, this is a nicely working stone. Brand new, the stone felt very aggresive, but after the first “familiarising blade”, speed went down. On the tested blades, the stone was quick in the beginning, but got noticeably slower as swarf and loading build up.

Comparison with the Diamond Matrix stone

Now, let’s compare this to the proven and excellent Matrix 4000 – after all, this is the main question here: is it worth it to upgrade?

Let’s take a look at identical condition microscopy pictures of the Diamond Matrix stone:

SEM micrographs of the Edge Pro Diamond Matrix 5 µm stone. Instrument: Zeiss GeminiSEM 560.

We can immediately make out a much lower diamond concentration.

This is further confirmed in the EDS analysis:

EDS analysis of the Edge Pro Diamond Max 5 µm stone. Instrument: Oxford Ultim Max  ∞ 40mm² EDS sensor. Note that our EDS sensor doesn’t show elements lighter than boron.

The view in the SEM is much more homogeneous than from the DiamondMax, with fewer “rolling grain” artifacts visible:

Edge quality looks pretty much identical, but the surface morphology is more homogeneous.

This is further reflected in the 3D height map:

The roughness is pretty much identical to the DiamondMax stone – I’d say there is no significant difference:

Sa	0.008447	µm
Sq	0.01094	µm
Ssk	-0.4306	–
Sku	4.170	–

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

Please check out my original review of the 4000 stone here:

A brief study on sharpening stones – Part 6 – Edge Pro Matrix Stone 4000 Grit (5 micron diamond, resin)

So, let us compare the results, side by side:

Comparison between the new DiamondMax 5 µm (left side) and the “old” Diamond Matrix 5 µm (right side).

The new DiamondMax stone definitely contains significantly more diamond. Moreover, it is build on the same “principles”, meaning it’s a very pure resin stone. According to the manufacturer, the resin hasn’t changed at all. The result is comparable in nature – the measured surface roughness is within the variance expected. The apex is comparable in quality. The DiamondMax feels ever so slightly faster, but I wouldn’t call it a significant difference. I feel like it looses more grains – this would go hand in hand with the manufacturers statement that it wears quicker, but also what we can identify as a slightly more irregular scratch pattern on a bevel due to rolling grains. Overall, I would say this is a minimal step forward in terms of speed, but it looses some of it’s quality by this. If I was you, I’d stick with the old Matrix 4000, this upgrade doesn’t look like it’s worth it.

Just like in the last review, I want to draw the comparison with what a pure resin stone can do – and include results from my 5 µm sharpening stone here:

SEM micrographs of a M398 edge finished with Dr. Marvs Scientific sharpening stone, 5 µm. Instrument: Zeiss GeminiSEM 560.

It has a slightly cleaner, less wavy apex line. The surface in the SEM is comparable to the matrix stones. Optically, it’s much more homogeneous:

Optical micrograph of the M398 blade finished with Dr. Marv’s 5 µm stone. Instrument: Marvscope

In the 3D height map, we can identify fewer scratches and an overall smoother surface:

The surface roughness parameters are lower:

Sa	0.006707	µm
Sq	0.008277	µm
Ssk	0.2270	–
Sku	2.808	–

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

So, with a cheeky smile from my side: if you are looking to upgrade your Diamond Matrix 4000, I wouldn’t. It’s a fantastic stone. The new DiamondMax doesn’t differ significantly but in price. My 5 µm stone gives a cleaner result, but instead of buying my stone, I have a different suggestion for you:

Spend that “upgrade money” on a nice dinner with a person who is important to you. It is better invested.

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 the brand new, just released EdgePro Diamond Max! Rumors of these stones coming have been floating around for a couple of months already, and I have been very much itching to get my hands on one of these. The Edge Pro Matrix stones (also sold by the producer, CGSW) are considered some of the best sharpening stones on the market – rightfully so! I had their 5 µm Matrix stone on the blog quite some while ago. It gives a fantastic edge, polishes the bevel finely and I only had two major issues with it: it is probably the most expensive sharpening stone on the market by amount of abrasive you are buying, and the low concentration made that stone very slow.

When they got launched in a silent reveal at the end of April, I didn’t hesitate a single second, eager to try it out and order 3 stones to Germany. Something I want to highlight here: the contact with the owner of EdgePro, Cody, was superb – I had a question about tracking and got a super polite, helpful email back. This, dear readers is why I advocate buying from small manufacturers, and ideally directly from them!

Just two days ago, Cody uploaded a video on his youtube channel explaining about these stones. The new DiamondMax stones seem to adress the issue of speed, albeit this comes hand in hand with a major price bump (roughly 20$ increase on the stones, bringing this 160 µm / 80 grit stone to 107$ before taxes / import duties if you buy outside the US). The abrasive layer is still very thin. According to the manufacturer, these stones now contain between 1.8 and 2.5x more diamond, depending on their grit!

Let’s take a look under the optical microscope!

Optical micrographs of the stone. Instrument: Marvscope

I absolutely love coarse sharpening stones under an optical microscope! There, one really can make out the grain and grain concentration. The stone has a high concentration of quite blocky diamonds, a natural appearance at that grit size. The grains tend to clump together in groups of 3-6 grains. In between the grains, we can see the white resin layer. Some much smaller, blue-blackish particles can be made out.

I do not own a comparable size Diamond Matrix stone (hold your curiosity until I get around to the 5 µm review, there I can do a direct comparison!). The producer of the stones seems to still be CGSW, and he is very curious about my sharpening stones. In this thread on the bladeforums, David writes:

“…Diamond Max series that didn’t go anywhere. I made 2 sets of Matrix stones with the most diamond in them that I could a few years ago. One for EP and one for me. They do cut a little faster but at the expense of wearing much faster. Even if they didn’t cost more they would be a lower value than the current Matrix stones so they didn’t make it to production.” Quote from user “Diemaker” on the bladeforums, accessed on Sunday, 24th of May 2026.

Uff. Okay. That’s a hardcore statement to make about a product that is yet to launch.

Let’s take a closer look in the SEM:

SEM micrographs of the EdgePro DiamondMax 160 µm stone. Instrument: Zeiss GeminiSEM 560.

Under the SEM, the blocky nature of the grains is further confirmed. Size seems to peak at 160µm, with the majority of grains slightly smaller (100-140 µm). It is normal that diamond powder is not a single size, a gaussian distribution is always expected. What I find very curious is the high amount of “voids”, where clear imprints of grains have sat before. This is the stone before use, and already a massive loss of grains can be made out. Zooming in on one grain, we can see that although the resin is confining the grain above it’s main diameter, it is already loose and there is some gap between the resin and the grain.

Grain adhesion is the major issue in most resin stones, and it becomes more dominant the larger the grain becomes.

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 EdgePro DiamondMax 160 µm stone. Instrument: Oxford Ultim Max  ∞ 40mm² EDS sensor. Note that our EDS sensor doesn’t show elements lighter than boron.

The stone shows the typical, very pure composition we already saw in the Matrix stones: There’s diamond in there, and an organic binder, with not much else. The black-blue grain we made out in the optical micrograph shows as an oxide-abrasive grain, mostly peaking on the Mg-Si-O channel. I would guess that this is some abrasive debris from their flattening process. It will probably disappear after a few sharpening cycles, leaving a pure stone behind.

The impression that the diamond grain seems to clump together a bit is further confirmed in this image – we can see small nests of diamond.

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.

Something that became immediately apparent when using the DiamondMax stone, and was already suspected from the SEM pictures: this stone looses a lot of grains! Let me show you what I mean:

Microscopic views of the loose grain /swarfs after 20 and 100 strokes with the stone. Instrument: 100x Macro Loupe on iphone 17 Pro Max

Already on the first stroke (edge trailing), one could feel how grains would jump out. I counted to 20 strokes, and then did a picture of the bevel with my phone. You can see a frankly absurd amount of diamond – and very little swarf. Over the next 80 strokes, the stone picked up some speed, producing a lot of swarf, but also loosening even more grains. I cleaned it off, applied new lubricant and the same thing happened. Initial, hard grain loss, followed by an increase in material removal rate once there’s a certain “slush” going on. I’m a bit stumped by this wear rate – and frankly, if you sharpen any expensive knife, you do not want this massive amount of loose grains potentially scratching the surface.

Let’s take a closer look at the result, and start with the harder steel – the M398 blade:

SEM micrographs of the M398 edge finished with the EdgePro DiamondMax 160 µm stone. Instrument: Zeiss GeminiSEM 560

We can see quite the ragged edge. The bevel shows clear signs of the rolling grain – deep scratches in the middle of the bevel, stopping and starting randomly.

The overall appearance is diffuse and sligthly chaotic – this is because the rolling, loose grain can jump around, but also move sideways and not only in the direction of the sharpening stroke.

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.

The surface roughness is pretty rough, too:

Sa	0.3708	µm
Sq	0.5017	µm
Ssk	-0.7942	–
Sku	5.777	–

ISO 25178 surface roughness parameters. S-Filter: 2.5 µm (gaussian), L Filter: 0.08 mm (gaussian). No F operation besides LSQ leveling.

Overall, I’m quite disappointed. Let’s see whether the stone performs nicer in a softer, easier steel, and take a look at the NitroV edge:

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

In addition to the very rough, broken up surface, we can also detect some splintered pieces of diamond that have embedded themselves into the bevel.

Optical micrograph of the NitroV bevel. Instrument: Marvscope

The surface looks a bit more irregular, with a massive amount of sideways or circular scratchmarks, caused by the grain rolling around freely in the abrasive/debris slush created.

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 deteriorates even more:

Sa	0.4595	µm
Sq	0.6215	µm
Ssk	-0.8645	–
Sku	5.439	–

ISO 25178 surface roughness parameters. S-Filter: 2.5 µm (gaussian), L Filter: 0.08 mm (gaussian). No F operation besides LSQ leveling.

Now, you might think at this point: why am I so disappointed? It’s a coarse stone, meant for quick material removal, and some grain shedding is expected, especially on resin stones.

The problem is: it’s not. It can be done differently, it can be done better.

Let me explain, and I’ll do so by something I do very rarely – a direct comparison. You see, I also make a resin stone with near identical grain size denomination, the Dr. Marv Scientific Sharpening stone in 150 µm. Let me pull you up an optical picture, side by side to the EdgePro Diamond Max in 160 µm:

Identical magnification shots of (first picture) the Diamond Max 160 µm and (second picture) the Dr. Marv 150 µm stones.

I will let you draw conclusions about the concentration yourself. Let us compare the results – this is the exact same M398 blade, sharpened with my stone:

SEM micrographs of the M398 edge finished with Dr. Marv’s 150 µm resin stone. Instrument: Zeiss GeminiSEM 560

The view of debris after 20 and 100 strokes:

View of the swarf after 20 and 100 strokes, sharpened with Dr. Marv 150 µm resin stone.

Optical micrograph of the bevel:

Optical micrograph of the M398 bevel. Instrument: Marvscope

And last but not least, the WLI results:

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 values being about 2.5x lower than on the EdgePro stone:

Sa	0.1481	µm
Sq	0.1981	µm
Ssk	-1.003	–
Sku	4.930	–

ISO 25178 surface roughness parameters. S-Filter: 2.5 µm (gaussian), L Filter: 0.08 mm (gaussian). No F operation besides LSQ leveling.

I typically end my reviews with a conclusion. I think none is needed here, but for completeness sake I’ll do one:

The DiamondMax 80 grit stone seems to have a high diamond concentration. It is definitively not the maximum possible. Some agglomeration is apparent in micrographs and chemical analysis. Grain retention is nearly non existent on the stone, with large amounts of wear and free-rolling grain induced results on the blade. The stone is probably the most expensive diamond stone on the market if one takes the very thin arbasive layer into account. Results are matching these findings – marred, rough bevels and a ragged, wavy apex. The initial quote I pulled from David (CGSW) on the Bladeforums becomes very true:

“Even if they didn’t cost more they would be a lower value than the current Matrix stones “

And they even bumped the price.