JKI 1k/6k diamond stone first impressions

HeavyHanded

HeavyHanded

Joined
Jun 4, 2010
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Very quick initial writeup for the diamond stone 1k/6k set offered by JKI. Have been looking at these off and on for a few years but never wanted to drop the coin. Came into a little mad money, picked up the pair. There is not a lot of info circulating re these stones, thought I'd share what I know so far.

Am not a big fan of the bonded diamond abrasives I have tried, so this was a leap of faith for me. Haven't had them very long, this is also a very preliminary review.

Initial impressions are that on budget stainless these are somewhat slow cutting compared to ceramic stones of comparable grit. Cut speed of the 1k is closer to that of a 2k maybe and the 6k that of a 10k ceramic. If applying a microbevel with the 6k you don't have to worry about removing too much steel too quickly.

Grind finish looks typical for the rated size.

Edge quality is very good coming off the 6k, still has bite. Used on an O2 chisel and stropped with some of my house Washboard compund it was shaving endgran pine to a nice wet finish. Not good enough for real fine finish work but plenty good enough for most chisel work - whittling armhair off the surface.

The stand alone edge off the 1k is maybe perfect for an EDU blade. Sharpened up a Vic utility knife and CS minituff in Aus8, with a handful of passes off a washboard charged with mud and swarf from the stone surface, treetopping leg hair with authority yet wicked catchy.

The bond material has enough "give" that both stones will just tolerate a backhone pass to finish. The surface is just hard enough that this is not necessary to get the best from the stone - so a bit of flexibility depending on preferences. I prefer to finish backhone if the stone will allow as it seems to make an edge that is that little bit more catchy.

The surface does not load much if at all as long as it is kept wet - actually better in this respect than some of my ceramic waterstones, needing only a little agitation with a fingertip to release the swarf. This is a major beef I have with a lot of the bonded diamond stones, so am very pleased in this regard. It is easy to keep the surface wet, and the composition does absorb a bit of the water - completely dry in under an hour if the surface is squeegied with the edge of your hand when done.

Wear appears to be negligible, but have not used them enough to get a feel for this. Using the suppled Nagura stone, a very thin tea (not mud) the color of the stone can be raised with a bit of rubbing. A bit of color also visible on the reclaimed swarf from the stone surface after several minutes of spirited grinding, though most of that is just swarf. Am going to use Barkeeper's Friend on the surface to unload it next time it is needed - surface reconditioning with an abrasive really should not be necessary, although it is recommended for best results, so loading and/or glazing must be a genuine factor over time.

I haven't used them on high carbide steel yet, but will do so in the coming days/weeks. I expect they will perform even better on the higher RC/high carbide steels. My hope in getting this set was to have stones that could perform well on ANY steel, travel well, last nearly forever, and be more user friendly and durable than diamond plates. So for now am concentrating on budget steels. The 1k is not aggressive enough to reset bevels if the edge has any appreciable wear, a coarse stone is definitely needed to complete this set, but at that grit level any SiC stone could easily stand in. The 1k can overgrind a fairly aggressive scratch, so an intermediate stone isn't needed. If a mirror finish is needed, some form of finishing stone, strop, lapping film will be a must. It is a true 6k finish, for most chores this will be more than refined enough, and on high RC/carbide steels I expect the scratch to be even less deep. A bright finish, but not mirror by any means.

So far cannot give an open-ended recommendation as I just haven't used them enough for the price. If they were less expensive by half it would be an easier call. That said, if you are already a fan of bonded diamond abrasives, these are worth a closer look. While a bit slow on budget stainless compared to some ceramic stones, they have very good feedback for stones of this type, make a very good quality edge with minimal fuss in terms of burring, both from abrasion and pressure, and hardly load in use. They manhandled the O2 1.5" chisel, which was another pleasant surprise and more testimonial to how little they load - with short work, the tea on the surface of the 1k was swimming with swarf. The 6k overground the entire bevel in under a minute.

I have had them less than a week. Stones are roughly 3"x8", splash and go. They come with a robust rubber base and nagura stone. More to come.


6k side view
xJvAkir.jpg

1k side
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washboard slush
E8GgarP.jpg
 
Ok, good. Those grits are too fine for my use. Do they offer that size stone in the 3-400 grit range? DM
 
Those do look VERY much like DMD resin stones. Though normally I would favor buying from JKI for the quality control and support alone the apparent markup in this case is astronomical. Even if JKI has these made with a superior formulation I have trouble seeing how that price is justified.
 
Mr.Wizard said:
Those do look VERY much like DMD resin stones. Though normally I would favor buying from JKI for the quality control and support alone the apparent markup in this case is astronomical. Even if JKI has these made with a superior formulation I have trouble seeing how that price is justified.
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I'm going to go out on a very thick limb here and say there is no way these are the DMD stones rebranded - Jon has been selling these for something going on 9 years, how long have the DMD ones been available? Plus the handling qualities don't sound the same - the German forum described water passing right through the bond layer and with these it rides on top.

I don't know myself if these can be justified pricewise though, which is why I'm just going to describe how they work and leave it at that. I believe Deadbox Hero was sort of in the same boat when he reviewed the Naniwa diamond stones.

That said, if they last 2x as long as a comparable DMT plate and are nicer to work with, then they'll be doing pretty good, not to mention the handling qualities. I've used a few bonded diamond abrasives and honestly didn't think highly of any of them, some of the resin jointer stones I've bought did just as well and at rock bottom prices, but they all came with limitations. Less than a week in and these are blowing away any of the others I've used. I expect to only get faster with them as I go.

Again, pricewise these are brutal. But I have several times that over in stones I use seldom or not at all anymore - time will tell.
 
HeavyHanded said:
Jon has been selling these for something going on 9 years, how long have the DMD ones been available? Plus the handling qualities don't sound the same - the German forum described water passing right through the bond layer and with these it rides on top.
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I did not remember that. The timing of your review made me think this was a newer product. Were these the original diamond-bonded stones marketed for knife sharpening?
 
Mr.Wizard said:
I did not remember that. The timing of your review made me think this was a newer product. Were these the original diamond-bonded stones marketed for knife sharpening?
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Yeah, the full history of these is over on kitchen knife forum, Jon had them made to his specs by a Japanese manufacturer after trying what ones were available at the time (pre 2010) and not being thrilled with the existing options.

They aren't Naniwa and I have no idea where they come from. I have decided a few years back, the only stones I'll scrimp on are combination SiC stones, the better waterstones I have weren't cheap, but they kick butt. Mid priced ones I don't use at all now except as weight to hold the lid on the hamster cage (she strong for her size!).

I've been looking at them off and on for years and sort of impulse bought them with some unplanned cash - I came into. Paired up with a disharp XC I hope these will handle all of my non-woodworking sharpening chores no matter the steel.

Jon sells a 300 grit diamond bonded stone that could replace the XC, but that one stone costs more than the 1k/6k combined...I'd need a lot more work than I currently have to even consider it.
 
More pics, not very good but interesting anyway. Low/side light you can see a pretty good concentration of diamond along all the high points in the stone. There are also a goodly concentration of what apper to be metallic/reflective mineral bits all over and through the stone. The ones along the high points show evidence of being scratched flat across the tops, so they are softer than/being worked by the blade steel.

I initially thought these were pockets of diamond, but the actual diamonds throw back no light unless illuminated from the side under low light.

Is difficult to get clean pics of the color variation using this microscope, these pics are not in the same class as the ones of the DMD stones on the German forum. Safe to say though that the composition is not the same.

Grind speed of the 1k seems to be increasing as I use it - more likely I'm dialing it in. Able to overgrind an XC DMT scratch using the 1k very rapidly. Need to do more work with the 6k. I do suspect whatever surface treatment these get during manufacture needs to be worked off/through to get the best of it. I might even lap the 6k with some loose 200 grit SiC.

Still no sign of them loading with use.

Sidelight 40x
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lights on 40x
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sidelight off 40x
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1k surface 20x showing reflective bits that are not diamond
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That's the funny thing with synthetic diamond vs. most other abrasives. They get more expensive the larger the grains are since they have to grow the grains vs. making a huge block and crushing it down to size like they do with silicon carbide or aluminum oxide.
 
HeavyHanded said:
Very quick initial writeup for the diamond stone 1k/6k set offered by JKI. Have been looking at these off and on for a few years but never wanted to drop the coin. Came into a little mad money, picked up the pair. There is not a lot of info circulating re these stones, thought I'd share what I know so far.
Click to expand...

YES. Thank you for the write-up! They sound just like I suspected in terms of speed, but it is seriously tempting to grab those now that I know what the surface loading situation (or lack thereof) is like.
 
There is NO way I'd pay that much for 2 synthetic diamond resin stones. I thought the DMT plates were too pricey and I'll not replace those once I wear them out. I see it's the going rate but I'll use a different stone type. This is just me. Thank you, this is a good discussion. DM
 
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One can get the equivalent of about 26 3"*8" pieces of 3M Diamond Microfinishing Film, PSA backed, for the price one Naniwa diamond stone. I wonder which would last longer?
 
Mr.Wizard said:
One can get the equivalent of about 26 3"*8" pieces of 3M Diamond Microfinishing Film, PSA backed, for the price one Naniwa diamond stone. I wonder which would last longer?
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The diamond films DO last a while if you are careful with them. Limited in some respects to what you can do with them. Great for sharpening smaller knives, have done many on my Washboard using a progression of 3M films. You can't go anywhere near as fast on them, and one or two nicks and the sheet's in trouble.
 
Mr.Wizard said:
HeavyHanded HeavyHanded Useful to know; thanks! Are you using Microfinishing Film or Lapping Film?
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Not sure what the difference is. I use the materials sold for fiber optic polishing, no PSA, 3 mil backing. Have used everything from 30micron down to .5, works great with a drop of mineral oil.

It is easier to nick than wet/dry, so I mostly use it with a backhone pass. It can last a long time if used carefully.
 
Are these diamond sheets available at ACE hardware stores? I'd need to handle them to determine if the backing was thick enough. 30u is at 350 grit, which is where I work. Thanks, DM
 
David Martin said:
Are these diamond sheets available at ACE hardware stores? I'd need to handle them to determine if the backing was thick enough. 30u is at 350 grit, which is where I work. Thanks, DM
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I have never seen them at any hardware store.

Honestly, at 30 micron you're better off with a Crystalon stone or coarse diamond plate. I picked up a 3"x6" sheet just to tinker with - it works but is not really needed for any steel at that grit rating. Maybe for cosmetic polishing the primary it would make sense.

This is the stuff, but when I bought it you could get single sheets:
https://www.fiberinstrumentsales.co...m-3x6-30um-package-of-10-sheets.html?___SID=U
 
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