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 Jende Resin 120 µm. I have no idea why it took me this long to get around making a review of a Jende stone – I even got asked by avid readers whether I have some conflict with them. Honestly? They never were on my radar, but by popular request (which in turn raised my interest) I ordered some. Jende is an american company and has been making sharpening equipment for quite some time already. My order shipped from their Taiwan factory, which is a pity – I had hoped that an American company would actually produce in America, but I guess this is not the case for the full range of products they offer.
Let’s take a look under the optical microscope!
Optical micrographs of the Jende Resin 120 µm stone. Instrument: Marvscope
The stone is a curious, yellow colour. It’s fixed to a steel blank, making the whole abrasive very heavy. We can make out parts that are very flat and even, and others where the stone looks a bit more porous. The diamonds appear very white in colour – this is quite curious, as most diamond powders are actually slightly greenish in colour. The size in optical micrographs looks to be a bit on the smaller size, but I always find it very difficult to correctly measure resin stone diamond sizes optically, as the resin covers the stone partially and contrast to the resin is also horrible.
Let’s take a closer look in the SEM:
SEM micrographs of the Jende Resin 120 µm stone. Instrument: Zeiss GeminiSEM 560.
The stone has quite a few different sized abrasives in it. We can make out large, flat chunks, but also many smaller, blocky, angular grains here. There’s quite a few voids, which have a “glassy” or smeared appearance to them – a sign that these are pores from the manufacturing process, and not lost grains. The resin itself looks like a phenolic type resin, with a very small, gritty look to it.
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 Jende Resin 120 µm stone. Instrument: Oxford Ultim Max ∞ 40mm2 EDS sensor. Note that our EDS sensor doesn’t show elements lighter than boron.
The EDS analysis shows that the large, flat particles are actually the diamond. They are well within their nominal size – so the appearance on the optical microscope was, as I postulated, misleading. From a chemical composition point of view, we can make out the diamond in some clusters – mixing could be a little bit improved if you ask me. The smaller, blocky abrasive grains are aluminium oxide – and they are very well distributed all over the stone, as well as much smaller than the diamond grit. There will be future reviews on finer Jende stones, it will be very interesting to see whether the Al2O3 is the same size throughout the series.
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 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.
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 Resin 120 µm. Instrument: Zeiss GeminiSEM 560
Overall, the stone did a decent job. The apex is refined, albeit not insanely sharp. Material removal was quick and consistent. The bevel surface structure shows a mix between real cutting action as well as ploughing of the grains, forming some micro prows and burrs. Some deeper, random scratches are visible.
Optical micrograph of the M398 bevel. Instrument: Marvscope
I’ve recently gotten access to a wonderful white light interferometer – a Zygo Newview 9000. I’ll try, as time permits, to include 3D scans of the bevel in future reviews, starting with this one:
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.
We can see the impression from the SEM pictures validated, but also get some quantifiable numbers. The deeper scratches are in a low, single digit micrometre range. I would say this is a decent result here, and something that can easily be fixed by the progression of grits.
Let’s take a look at the NitroV edge:
SEM micrographs of the NitroV edge finished with the Jende Resin 120 µm. Instrument: Zeiss GeminiSEM 560
The softer steel with a lower carbide content shows a higher amount of deep scratches. Moreover, the apex is not very well defined, with a ragged line over the whole blade. Some cracking near the apex can be spotted on the more detailed pictures.
Optical micrograph of the NitroV bevel. Instrument: Marvscope
The optical micrograph confirms this. Larger breakouts, up to several 10 µm are visible. The bevel overall has a less consistent appearance. Some burrs can be detected out of the focus plane.
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 3D surface data further confirms this: we can see some deep scratches, reaching into the 10 µm range. Also, more scratches at 90° to the predominant scratch direction are visible. This is very interesting, as I vary my sharpening approach by this angle: I typically start at an angle 45° to the apex, until all the grinding marks from the previous stone are gone. Then I switch direction by about 90° – so that the grinding marks once again are 45° to the bevel, continue until all grinding marks are gone and then go to my testing procedure of alternating strokes on each side. Overall, that’s typically at least 100 strokes per side – that a deep groove “survives” to be visible is quite astonishing. I would guess that this is either caused by loose, rolling grains or maybe by some agglomerated nests of diamonds.
Overall, the Jende resin stone is a decent stone. I found the feedback pleasant, although the stone stinks really badly right out of the box. Material removal is consistent after an initial drop of, it’s quite fast and a good choice to set the initial bevel. It has strong competition in it’s price range – especially by the Ukranian sharpening stones from PDT. If you are looking for a more high quality option, there are some around on the market.
