The Greatest Sharpening Stone in the World

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You need to be able to go A to B, B to C, C to A. The point is that any pair that mates in all orientations does so as a spherical interface with flat being a spherical interface of infinite radius.

1.So if A mates to B , but A is concave and B is convex

2. A mates to C, but A is still concave.

3. You need to have a way to put B against C to see that the two convex surfaces don't mate.

As I said, you can get two stones mating and then verify that the radius of the interface is large enough to be reasonably flat with a straight edge or other reference, but this is different than the 'three stone' method.
This doesn't make any sense to me, since it doesn't account for D, and the fact that A and B (or C and D) can't interface with each other... I would never figure out the three shells :(

But I understand it after drawing out the different permutations. Maybe I have a mild learning disability, but this makes a lot more sense to me than your written argument:
69178253-BF64-42FF-870C-E211D9425DDC.jpeg
 
53FAAAEA-2ABF-4451-9C44-A998F17BE8CF.jpeg

Here's my thinking: if you sharpen on only one side of one stone then try to flatten with the other untouched sides (first line, pink progression) you end up with one stone convex on both sides and one concave.

But, if you interface them following the progression on the second line, then sharpen on the most convex side of the second stone, you can flatten them back to zero (third line).

This is all theoretical of course. I'm assigning the amount of sharpening wear an abstract value of "1", assuming both stones are equally hard, and interfacing any two sides will result in a perfectly symmetrical addition/subtraction.

I understand this two stone/four face method wouldn't work with two different stones, but it might be good enough for two identical stones. Especially coarse stones where absolute flatness isn't so important.
 
But much more careful use of the coarse stones do, which just as much as keeping them so flat is not important, is usually why we won’t bother to much. But you would have to.

I think @M1k3 idea of introducing a crystolon into the mix might be time/worry saving so worth it’s dime.

🤷🏻‍♂️
 
With India and Crystolon's and worrying about how you're going to flatten them.... don't. Unless you're sharpening professionally. Or obsessively. Or allowing every line cook who kinda sorta knows how to sharpen to rub their knife across the stone, it's going to dish obscenely slow..
 
I wrote Nanohone customer service regarding the NL-4 and Crystolon/India stones. They said it wouldn't be a problem. I used one of the NL-4's for a week and didn't destroy it flattening India's and Crystolon's. Wasn't heavy dishing... but it worked..

I can imagine this. Diamond is the only thing that really makes a dent on them, it's just not worth trying to do it on atomas to dished stones. I haven't found Crystolon to be much use in trying to flatten ones that do need it. They kinda just bounce off each other, and polish the other stone without abrading it, and belts obviously do the same. Lots of pressure on paving slabs can work.

Interesting also to note - Crystolon stones are softer than Indias in terms of their structure, and will dish a little if used in exactly the same way. Also Coarse Crysolon/India are softer than the Fine versions. I assume this is something to do with not wanting the stone to completely burnish if using with heavy pressure.

Really though, as you say, worrying about flattening India stones is not anything that should occupy one's time unduly. They basically just don't dish with normal knife use.

---

Any idea how easily scratches from a medium India could be removed by the GS500?

I can check for you - I have both. Would you like me to use oil or water with the Med India?

While I'm playing my silly game of 'Greatest Synth Ever'... SG500 would probably actually come in at No.2 - every time I use it I'm baffled by how they've made it so good. With the Ouka taking the final spot on the podium.
 
It's a nice flattening plate. Not sure of longevity, I only had it for a week.
That's what's holding me back from buying it...the longevity issue. There's no question that Nanohone's flattening plates are good, but it's a lot of money compared to the price of an Atoma replacement plate.

Or to put it another way, for the price of a Nanohone flattening plate I get a lot of Atoma replacement sheets.
 
dumb question, but this is the one you're talking about, right?

1645788472561.png


just asking because the colors don't seem quite like yours (yellow and orange-brown vs brown and dark-something), and i'm not familiar with norton's lineup at all.

and again, it works well as a water stone after initial degreasing? i don't want to use oil. i sharpen in the sink with water.

do you have to soak it much?

thanks!
 
dumb question, but this is the one you're talking about, right?

View attachment 167350

just asking because the colors don't seem quite like yours (yellow and orange-brown vs brown and dark-something), and i'm not familiar with norton's lineup at all.

and again, it works well as a water stone after initial degreasing? i don't want to use oil. i sharpen in the sink with water.

do you have to soak it much?

thanks!

That’s it indeed - the IB8.

They changed the various colours of coarse/med/fine from time to time, and I think also in different markets. But yeah - those are the current colours.

If it’s oil filled - you’ll want a day or two soaking in degreaser, might need to change it. But after that it’s a splash and go to use with water or oil.
 
thanks, just ordered one.

https://www.ebay.com/itm/373416847178
that's the cheapest one i found in case anyone else is looking. $28. can it really be found for $20 or less rn?

Looks like this guy on amazon for $22. Just threw it in my cart - I need to sharpen up a ridiculously dull hatchet tool thing I use in the yard. After I'm done hacking at it with a file I think this stone will add the finishing touch.
https://www.amazon.com/Norton-61463...n+india+stone+61463685565,aps,247&sr=8-1&th=1
 
@spaceconvoy Here's another way to think about it. When you rub two stones together in a random way, the stones will tend toward an equilibrium state where the convexity of one (if present) matches the concavity of the other. (They might also just be flat, but they might not.)

If you have two double sided stones, it could be that one stone is convex on both sides, and the other stone is concave on both sides. Then if you rub one stone against the other, you'll stay in that equilibrium, no matter which sides you're rubbing together.
 
Would you like me to use oil or water with the Med India?
I'd love to know how it works with water, thanks! Are you expecting there's a noticeable difference? Maybe something to do with the amount of swarf suspended in oil vs water.

If you have two double sided stones, it could be that one stone is convex on both sides, and the other stone is concave on both sides. Then if you rub one stone against the other, you'll stay in that equilibrium, no matter which sides you're rubbing together.
Yes, that's true in the absence of any further dishing (as illustrated on the first line in pink). But we can take advantage of the fact that dishing is a continuous process and keep alternating between stones, sharpening on the convex one until it's concave, then interfacing them to make the other stone convex, back and forth until they're completely worn down.

The disadvantage is you'll always start sharpening on a convex surface, but that doesn't seem like a big deal to me since I don't care about precisely flat bevels or polishing. I just want to know that a few years down the line I'm not left with something unusable that's become very difficult to fix.
 
I'd love to know how it works with water, thanks! Are you expecting there's a noticeable difference? Maybe something to do with the amount of swarf suspended in oil vs water.


Yes, that's true in the absence of any further dishing (as illustrated on the first line in pink). But we can take advantage of the fact that dishing is a continuous process and keep alternating between stones, sharpening on the convex one until it's concave, then interfacing them to make the other stone convex, back and forth until they're completely worn down.

The disadvantage is you'll always start sharpening on a convex surface, but that doesn't seem like a big deal to me since I don't care about precisely flat bevels or polishing. I just want to know that a few years down the line I'm not left with something unusable that's become very difficult to fix.

I think relying on dishing from sharpening to correct things is kinda iffy. The point of the 3 stone method is that you KNOW you're getting a flat surface. But if you don't care about a bit of convexity/concavity, then sure, do it like that. If it starts getting out of hand, hit them with sandpaper on a flat surface, or bring another stone into the rotation. It's not like they'll suddenly become unfixably convex/concave all at once.
 
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I have had some success flattening using a diamond plate, one I don't care about.

This stone here on the left had been freshly lapped because it had started to get low in the center. Kind of selective material removable from the surface of the stone. I don't need them to be perfectly flat.
I flip the stones when they get to much dish to deal with and when both sides are dished it's time for new stones.

 
I'd love to know how it works with water, thanks! Are you expecting there's a noticeable difference? Maybe something to do with the amount of swarf suspended in oil vs water.

Will report back!

I'm still to get my head around the physics of why oil is better for sharpening. It has improved every single stone I've tried it on (including jnats) in terms of cutting speed and performance, but doesn't really polish very well I've found. Will give both a go and report back with some pics.

FWIW - if an India stone isn't 'pre-filled' with oil, then you can chop and change between oil and water quite happily. You can do that on most stones actually.
 
I'm still to get my head around the physics of why oil is better for sharpening.
I've had this same question.

Somewhat related. I used to use W/D paper dry on steel. I was asked why I didn't use water with it.
I had tried it with water and also with my oil stone 'go to' propylene glycol, neither of which seemed to improve things at all over dry. I was certainly willing to try other lubes and WD40 was recommended. This made a huge difference for me.
 
Whooo :) I don`t like Roszutec at all, but maybe the 5 i checked are bad. Anyone tryed a frankonian hone ? My sharpening teacher talked me into one (if i ever find one :( )

SirCutALot
 
For lower grits, oil with maybe some thiner, is recommended as best practice.
For finer stones, something like WD40 is considered to be better for performance. There were some very fine India stones available at times, but they aren't easy to find. So this would be more for fine naturals.
And indeed WD40 works very well for sandpaper.
 
Whooo :) I don`t like Roszutec at all, but maybe the 5 i checked are bad. Anyone tryed a frankonian hone ? My sharpening teacher talked me into one (if i ever find one :( )

SirCutALot
Funny I know 5 Rozsutec and all are good. Maybe it's just a question of sharpening technique or sharpening philosophy? That the technique or philosophy sometimes doesn't fit the stone...

Hardly anyone here will know the Franconian hone... it's more well-known in a certain German forum. There is also someone who prefers a cheap deba for tasks like deboning poultry - I assume you know him?!
 
My stone arrived today - good thing they’re indestructible since Amazon just threw it in an unpadded plastic envelope.

I have a yard tool that had never been sharpened with an edge that looked like this (this is a different hatchet but equally dull). Literally a 4mm flat “edge”.
A773303C-3B2E-47FF-94EC-EB1CA7C4AD0C.jpeg


20 minutes with a mill file - and omg mill files are freaking awesome - and 15 mins with the coarse side of the india stone, and I have an edge that can actually slice paper! All ready to tackle some intrusive tree roots tomorrow.

This is an extreme example but I can see where the love comes from for this stone on super dull knives. You can see leftover sharpie marks on the bottom of the edge - the stone did a great job of chewing through the high spots from the file work and giving me an actual edge.

24AC2D1D-1DC6-41C6-B3A7-A8492566564A.jpeg
 
My stone arrived today - good thing they’re indestructible since Amazon just threw it in an unpadded plastic envelope.

I have a yard tool that had never been sharpened with an edge that looked like this (this is a different hatchet but equally dull). Literally a 4mm flat “edge”.


20 minutes with a mill file - and omg mill files are freaking awesome - and 15 mins with the coarse side of the india stone, and I have an edge that can actually slice paper! All ready to tackle some intrusive tree roots tomorrow.

This is an extreme example but I can see where the love comes from for this stone on super dull knives. You can see leftover sharpie marks on the bottom of the edge - the stone did a great job of chewing through the high spots from the file work and giving me an actual edge.

Looks really good. Did you use water on the stone?
 
@cotedupy I wouldn't believe they were good if I didnt have one myself.

I bought one maybe a year ago. Just because it was cheap, and I was curious. It totally surprised me. The speed is quite fast, it's quite hard.

I liked it so much I upgraded to the larger size. I just wish I could get one that is a little wider. I eventually found that I like to use wd40 or oils with a similar viscosity. They tend to work best in my experience, but ymmv.
 
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