New JNS Synthetics: Coarse 220, 400, 800

[supersum1]

JNS just release what looks like a new set of course synthetic stones on their website:

JNS 220 Coarse

JNS 400 Coarse

JNS 800 Coarse

They also posted some images and videos of the new stones on their Instagram:


I wonder how these new stones will perform compared to other coarse stones by JNS (looking at their 300 and 800 matukusuyama) and other manufacturers.

I'm excited to hear about the impressions of the KKF community over the next few weeks as these stones get delivered.

 

[blokey]

Interesting, seems like a full WA powder stone in description
http://www.matsumi-abr.jp/en/bi_wa.html

 

[ScharferMax]

As the subject of coarse stones is often a highly debated topic, I take advantage of my recent acquisition of JNS 220 and JNS 400 to share my experience in this thread.

The reasons that motivated my choice are multiple: after owning and testing numerous stones for repairs, thinning, and more recently regrinding and polishing, I always encountered the same dilemmas: the fast and softer stones needed to be flattened every 2 minutes, and the harder, more precise ones were also slower. Of course, they're diamond/Atoma type stones which seem like a good compromise, but lose efficiency with wear.
In short, I hesitated before investing in these two stones, but the description was promising and I had already had good experiences with JNS, so I went for it.

Both stones are of good size (approx.1kg, 200X85X30 mm), they come already sealed and relatively flat. A quick pass on a diamond stone was enough to get them ready for action.
For a thinning operation, I started with the 220 grit stone. After a few passes, a slurry develops, but quite reasonably.

Very quickly, I am convinced by the very pleasant feedback which reminds me of that of a Cerax 1K (soaker), quite chalky, slightly coarse, but without any unpleasant gritty/sandy sensation. You can feel that the stone is doing its job. Here is the scratch pattern:

The logical next step is to use the JNS stone to refine the scratch pattern... Again, the sensations are good and similar to the 220, but the grit is of course finer and the feeling is logically firmer without being hard. Here is the scratch pattern:

So, the verdict:

The positives: the feedback, the size of the stone (which partly compensates for its higher price compared to competitors), the fast cutting, the slurry management.

The negatives: one must avoid applying strong pressure on the 220, and preferably use the entire surface of the stone as much as possible, as the risk of dish remains significant, especially if, like me (a beginner in polishing), one stays too long on the left or right side of the stone to maintain consistency as much as possible.

In any case, they're worth a try if you're looking for an alternative to the popular shapton and naniwa models.

Hope it helps!

 

[Uncle Danny]

Thanks for the feedback

 

[panda]

anyone else have the 220? from the video reminds me a lot of what I imagine an extra coarse chosera would be like.

 

[brownsugar69]

How does the JNS 220 compare to other coarse stones like Debado LD21 or Imanishi pink brick?

 

[NickMinton]

How does the JNS 220 compare to other coarse stones like Debado LD21 or Imanishi pink brick?

I have all three stones and I would describe them as a harder profile

They dish much more slowly but cut less than debado 180’s

 

[MartinJ]

Hey everybody!
I have a few heavy reprofiling jobs to do, mostly on german / soft stainless but also on a couple of carbon san mai.
Was wondering if this jns 220 would do the trick cause neither the shapton pro 220 nor the king 300 seems to eat metal at a convenient speed.

Also my atoma 140 is worn out now and i'm a bit disappointed with the longevity for the price.
I was thinking maybe a 20 bucks manticore could flatten my stones (starting with king 300 and up to chosera 3k) for way less money. Do any of you use manticore for flattening other stones?

 

[ScharferMax]

Personally, I have very little experience with stainless steel blades, but I own and have used many models that are frequently mentioned on the forum, and the problem is always the same: the balance between abrasive power, hardness, clogging issues and more or less pleasant feedback... It almost always comes down to a compromise, and no stone has convinced me 100%.
I'm not sure what you mean by "heavy reprofiling," but for thinning or preparing the geometry of a blade for a final polish on a jnat, the best compromise was the NSK model, though it can seem costly depending on budgets and goals... And especially, its ability to remove metal greatly depends on the preparation and maintenance of the stone, as shown in videos on the brand's channel. Regarding the JNS, it is necessarily softer, will require more flattening, and has a very pleasant feedback. I have two und like them for polishing jobs, so if you're interested, don't hesitate to send me a DM.