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.