Curved sharpening stones

[KL27x]

I've had some discussions last year that were related to this. Some thing about the burs, and how to get sharp edges. Ebastler comes to mind. I don't remember who else was involved. This is also something maybe my buddy coppercone2 might like to see, based on some of his past posts.

I finally made a video. I don't have a YT "channel," and I'm not trying to make one. I have a job, fortunately, seeing as my YT channel has only 1 subscriber (Does YT automatically give you 1 subscriber for yourself? I have no idea why I have a subscriber, at all. I've never published anything on this account).

Anyhow, this is just a video I made to show some convexed stones and a quick demo on how I use them. Requested by some random folks on reddit. But they asked nicely enough. I don't talk in the video. My sinuses are messed up, my jaw is too big, and my tongue is two sizes too fat for my mouth. So I don't talk in the video, but I added some captions. I spent a couple hours at least, making it. I thought I'd at least share it with 3 more people, here.

https://youtu.be/Pjfv1gRGtQM

Oh, the request was specifically just to show what I was doing. So maybe a tiny bit of background.
The curved surface reduces the contact area of the hard (non slurry/lapping stone). This increases cutting:burnishing. This make the soft arkansas sharpen, efficiently, without making bur, and without dulling the stone over time. I never had to do anything to these stones to maintain them. No flattening, no silicon carbide power, no microbevelling. This produces and/or maintains a razor edge without any other stones and makes a hard edge every time. You can't overdo it and soften your edge. The stones maintain shape by how I use them, no extra effort involved. (As long as I don't have to sharpen a pile of drill bits or 1/4" chisels at a time).

[ralphrmartin]

Where can one buy such stones? I can't seem to find anything like this in the UK.

[Gregg]

Here is a very interesting video with electron microscope pictures of burrs etc. 
https://youtu.be/RkYrpFGS5bY?list=PLFA60459F187488EF
Personally I find the Wicked Edge sharpener the best I have found (but it is pricey)
https://wickededgeusa.com/

[KL27x]

Where can one buy such stones? I can't seem to find anything like this in the UK.

First off, I'm thankful that anyone posted anything at all, to this. I was resigned to having put out a matza ball for which no one cares. So thanks for that, Ralprmartin, Gregg. And T3s, thanks for the thanks.

Answer: I don't think you can buy an arkansas stone like this from a store. (And I highly recommend soft arkansas stone for this).

What I did was buy some diamond plates for $4.00 each from Ebay China. I suggest 240ish the way to go for a soft ark. Then you use your eye.

People today stress out over how do you make sure it's "perfect?" There is no perfect. The stone will take the shape of how you use it. And the only reason (IMO) that it is curved in the long axis, at all, is just maintenance. If you take a stone nearly flat (or even flat) in the long axis, and you try to maintain the shape like that through use, your margin of error is tiny before the natural wear causes localized dips. If you start with enough curve for that material and how you use it, you will have the same error/tolerance in how it wears, but that shape you are aiming to maintain is curved enough where you don't get dips or "reverse curves" in the stone through this margin of tolerance/error. It is off by just as much, but it's still positively curved, everywhere.

As Jarrod says, "there's something magic that happens when every part of the stone can positively touch every part of the bevel."

If you curve the stone too much (I have experimented with that), what happens is you just end up using a smaller area of the center of the stone, because your wrist/arm/overall-movement range is not enough to use that whole curve efficiently. And the stone will wear down to the flatter shape, naturally. You're just getting it roughly into shape with the diamond plates. It's not, as we say, rocket science!

A 240 grit diamond plate makes quick work of the soft ark. Not a big thing. Just do it under running water.

This is really awesome for knives, esp. Because when you do the belly to tip, you start on the side of the stone and end up on top. That follows the edge automatically. You don't have to chicken wing your elbow out to follow that curve. It's like using a rod, but one where you have more area on top to not round off the tip. 

This curve doesn't make the arkansas magically able to do anything, though. On blade with a large enough bevel area and/or hardness of the steel, you will exceed the limits at some point. E.g., I can't do the whole bevel on my 3/4" chisel, for instance; I'm just sharpening the edge bevel of the compound bevel. If I try doing the whole bevel, I can feel the metal start to glide over the stone. In this case, if you feel it's not cutting well, stop doing it! You're wasting your time, and this will glaze the stone, and then you have to do something to get it working, again. Just go to your coarser stone at that point.

The other no-so-obvious benefit is that the oil stays on the stone. You don't need as much. When you sharpen a straight edge on a flat stone, you squeegee the oil back and forth. It is messier and or takes more frequent application.

[ebastler]

Hmm, not sure it was me participating in the original discussion you are referring to, but I am curious now. Would love to watch the video, but Youtube apparently does not know my age, and I like the idea of keeping it that way.

KL27x -- any chance you could remove the age restriction on that video?

[KL27x]

Yeah, sure. I just did it cuz all the warnings YT gave me. I don't think I will get fined for this. Try again in 1 minute.

[ebastler]

Thank you, KL27x. Watched the video now, and learned quite a bit. (About sharpening techniques, and the fact that sharpening stones can be a collectors item. ;-)  But I am not a knife and sharpening afficionado, so it must have been someone else in the original discussion. Hope they find this thread!

I very much enjoyed your video style, by the way. Keeping it quiet, with just the work sounds and the text in captions, totally works for me. And you found a very nice balance in the texts, keeping them succinct, but informal and colloquial. 

[KL27x]

I might have been exaggerating a little about that prior discussion, to give me a reason for posting this in this forum.

The thread got around to the question of what the bur or wire edge is. It started with the quality of drill bits, and how most of them will have a bur left on the edge, even the expensive ones. I think you were in that thread? You're a machinist by either hobby or trade, no?

Collector items? Yeah, I went a little deeper into the rabbit hole than I intended. I got some nice pieces of hardwood for Xmas back when, and wanted to do something with it besides making a box. Which I also did. And thanks for the part of that I will choose to take as a compliment to my handiwork.

[eKretz]

You're probably thinking of me. And my big gripe about the video is going to be machinist related. Did you really have to use a precision square to rub against the stones to show convexity?! I legit cringed! 

[tautech]

Yes well it's interesting what stones are accepted for each job and while an ordinary flat bench stone is perfectly suitable for the vast majority of tasks yet some will still try and reinvent the wheel.
In my inventory of stones all are flat faced and the only ones with curves are curved edge slip stones acquired primarily for deburring outside ground gouges.
They're the only stones I use that need oil as they came oil impregnated whereas my main Crystolon/India combo stone lives in water as it's a lot less messy to use.
With practice of good sharpening technique a stone face can be kept near perfectly flat and across it if anything it's preferable to have a minute dish especially for sharpening a 'smoothing' plane iron where on wider timber you don't want a perfectly square edge as it leaves lines on the timber. A shooting plane iron OTOH should be wider than the work so it can and should have a straight and square edge.

For portable stones my dad used 3" dia round 'spit' stones that you could comfortably keep in your pocket and a juicy spit was all that was needed to use it anywhere at all. He walked everywhere around our land carrying his grubber to grub out any weeds and many of them were woody so keeping a good edge on his tools made the job easier. A knife or an axe got a rub with it too as required. As the edges it was used on were curved it never mattered if these round pocket stones got dished faces after years of work.

All this talk about burrs, if the burr is excessive then the edge has been sharpened too far....simple user error yet the forming burr is a sign that the edge is fully sharpened and then the burr can be removed by at least a couple of methods. Razors as many know were finished with a leather strop that served to completely remove the burr by folding it back and forth as well as polishing the new edge even sharper. Tools like a plane iron or wide chisel can be addressed in much the same way however tradesmen that use these sorts of tools have tough coarse hands and a freshly sharpened tool edge can be carefully wiped back and forth along the hand to wipe the burr off.
With a stone each side of a freshly sharpened edge can be drawn away alternatively to effect the same process as stropping and folding the burr to and fro.

I easily make do with just 2 stones sharpening all manner of edges, only a flat bench Crystolon/India Combination  and a radiused edge slip stone.
ymmv
https://www.nortonabrasives.com/sga-common/files/document/Catalog-SharpeningStones-Norton200.pdf

[KL27x]

Did you really have to use a precision square to rub against the stones to show convexity?! I legit cringed

Oopsie; eKretz vs ebastler. My bad and apologies to both of you. My hard disc filled up and started to corrupt decades ago.

I'm not a machinist by any means, but I do I love my machinist squares. I was mindful to not actually rub them on the stones. But I can see why even that would get your hackles up!

Tautech, I agree with everything you said on the surface. And I'm not going say anything to contradict it. I will just clarify that I use india and crystalon, and these (as well as most other synthetic stones) are designed to be used flat. Indeed they work excellent when flat. In fact, the crystalon won't work if you try to convex it. It will just waste and crunch away until the surface is closer to the shape of your blade.

In fact, I would be fine with only an india for the rest of my life. It's the only bridge I probably would ever really need between power grinders and a good edge. I think Norton solved the sharpening stone problem what, 70 years ago or w/e. The rest is capitalism.

So why? Partly it was curiosity. Arkansas stones (not so much from arkansas, but probably from Turkey and England and other places) were used in antiquity. And it was named the razor stone, or novaculite. I've searched for pictures of old sharpening stones, say from Roman or medieval times, but I couldn't find anything. These guys didn't have Norton india stones to do the actual sharpening, and they didn't have diamond plates to refresh the surface. I imagine if they were lapping the on float glass, there would be some reference to it, somewhere.

Also these guys had to sharpen swords and whatnot, longer than the width of a sharpening stone (you would assume, anyhow, lol). Even in Japan, the land of waterstones, I have found that the traditional way swords were sharpened with rounded stones. This has been handed down from the guys who actually did this. Some ancient swords were essentially straight, some even a bit recurved. (Slurry/lappy stones work best IME on straight blades that aren't too long, or even better kitchen style knives with have a gentle curve approaching straight; not so nice to sharpen say a skinny 8" carving knife or boning knife that is very very straight and long. On a flat soft ark, even worse. Bad times. That might just be me.)

There is also, according to Jarrod, this idea that all of the cutlery and razor manufacturers in Solingen, Germany, use curved stones to hand sharpen their products for centuries. I won't call that a fact, but this is what he claims is told to him by Dovo workers. And I find it works, with the soft ark, very nicely. Lots of benefit. Some are not so obvious.

[tautech]

First I should qualify my remarks as a ex qualified tradesman carpenter also with a lifetime of rural living where a decade or two back we had 4 generations all living close by with whose experiences to draw on.

It is quite correct other stone styles were used historically for sharpening long blades and as a child I remember an oval one with a wooden handle used for sharpening scythes before the days of even horse drawn hay mowers and even dreams of grain headers.

I've ruined a bench stone or two in my apprentice days with incorrect use style and dished them end to end and side to side much of it due to using a honing guide for plane irons and chisels whereas careful handheld technique to use the stone's whole surface far better preserves its trueness.
I also have a very fine natural Arkansas oil stone that is so fine that it's only good for polishing to a keener edge but it's so slow cutting I now hever use it. Also of interest is my grandads cut throat razor mud stone, a water stone and again another that is very fine but also soft so cannot be used for narrow tools as they will dish it badly.

Nice discussing these things as it helps share our knowledge. 

[KL27x]

I also have a very fine natural Arkansas oil stone that is so fine that it's only good for polishing to a keener edge but it's so slow cutting I now hever use it.

That's what most Americans would think, as well. My first Arkansas stone sat in the bottom of a toolbox for 10-12 years, untouched since the first week after buying it. I had the same thought as you. It was pretty close to useless.

But the way our fathers could do anything they needed with just one india stone, I suspect our farther removed ancestors made these novaculite stones do way more than shine a bevel. I bet they were a very good and practical sharpening tool, because they can be; I have proven it to myself. I suspect there are plenty of Dovo workers who would think the same.

And if they CAN be, and if there was no Norton, Shapton, etc, then it must have been. The shape and technique changes how the stone functions. Our ancestors weren't worried about messing up their shiny Spyderco. They were sharpening stuff to survive, and their days were too busy to waste time, adding a novaculite stone to some kinda "progression." This was a valued trade item, not a time-wasting hobby stone. They were sharpening, in my imagination, all manners of tools for woodworking. Hoes, froes, adzes and weird stuff we never heard of. Because we have tractors and chainsaws and lumbermills.

This is not to say you can't get these stones to sharpen at all when they're flat.

[eKretz]

This is a very wide ranging subject. Books have been written about it and not covered all the vagaries. A few notes:

India hones have been around much longer than 70 years. I own one that's marked with a 1908 manufacturing date, and it's by no means the first.

Very fine Arkansas stones (translucent, black) are meant to be used as a final step in the sharpening process that only just smooths the apex of a blade. They aren't meant to remove much metal.

There are many and varied compositions of hone and stone with wildly differing binder strengths. The razor hone that turns to mud is a good example of the softer end of the scale. Black or translucent Arks are a good example of the opposite end. There are several factors that play into which end of the spectrum is better for a certain use - hardness of the material being honed/sharpened, surface area in contact at once, what stage of sharpening, etc.

[KL27x]

Hmmm. Ok. Lemme try a logic game.

If you assume that this particular tool (i.e. soft ark) is best-suited to this particular niche (i.e. shiny up a bevel, add a microbevel, or cheesegrate/lap-it-to-get-it-to-work-almost-as-well-as-way-better-alternatives-but-use-it-anyway-because-of-tradition) which we have put it in, presumably due to all the new and shinier (and cheaper and/or more profitable?) tools which have been added to our arsenals since at least 1908 or earlier, you might be getting shortchanged.

Is this even the traditional way to use it? Or did we invent this practice/methods for some other reason? Such as the invention of the diamond saw making perfectly flat and very nearly rectangular slabs of this stone the easiest way to produce them? Perhaps the first generations to buy these perfect slabs, maybe they immediately "fixed them?" Then a generation of humans grew more fond of the "new car shape" than they had need for this tool to actually be effective?  By this time, synthetics might have taken over the market, and these stones might have started to be shelved, anyhow? Or become collector's items?

While the true craftsmen in Solingen Germany quietly continue to find this stone to be one of the best tools for hand-sharpening despite all the new and shiny? 

Despite the time I invested into the fancy wood mounting systems I made, mine are not collector items. Everything there is for utility, once I figured out that these ARE going to be my main method of sharpening, due to being actually more practical for me, all told (well, to be more specific, I mean for blades which require to maintain very keen edges; this method is incredible for maintaining a keen and durable edge, all by its lonesome. Amazing. Not that it makes a sharper edge than other methods). I have used my india only twice in the last 2 years. To sharpen drill bits, and to sharpen a friend's brand new knife that came with no edge. The bits I added were added to get the right height/grip, add utility with the endcaps, clamping points, ergos, et al. That was kinda satisfying in itself; it felt like it was in my DNA to haft stone to wood, like pre-humans have done for like 1 million years or something like that. 700K maybe? I forget what the stone age was.

[ebastler]

While the true craftsmen in Solingen Germany quietly continue to find this stone to be one of the best tools for hand-sharpening despite all the new and shiny? 

I‘m afraid they are not that traditional in Solingen. They introduced water-powered wheels a few hundred years ago, and have progressed further since. ;-)

[KL27x]

While the true craftsmen in Solingen Germany quietly continue to find this stone to be one of the best tools for hand-sharpening despite all the new and shiny? 

I‘m afraid they are not that traditional in Solingen. They introduced water-powered wheels a few hundred years ago, and have progressed further since. ;-)

Well, notice wheels aren't flat, BTW.  But are you suggesting that true modern craftsmen, construction workers, capenters, razor makers, leather workers, butchers, chefs, and tailors, all buy Tormeks and/or send their stuff out to professional sharpening services, now? Or they find that 5 lbs of stones and a pond/bucket and frequent maintenance/flattening to sharpen a 3 oz knife or chisel is the most practical way to get their end results? Or is the power grinder and the Norton india this latest advance beyond the water-powered wheel, maybe? Those are both very useful, those last. Can't not have those, I admit, and they can do double duty to keep keen edges. And I guess you can say the india can replace the soft ark. But there are still advantages to the soft ark. The waterwheel is today the main tool used for shapening, if you count all the disposable stuff we use now. Razors and box cutters and scalpels and exactos, and on and on. There are still people/professions which need to resharpen things, but a waterwheel might not be a recoupable initial investment, nor maybe portable enough for the task! Or maybe not worth the space!

I just feel like after trying this, that humans have largely forgotten how to use this tool. 

[tautech]

Or is the power grinder and the Norton india this latest advance beyond the water-powered wheel, maybe?

Water driven wet stone ? That's a bit flash !
All the ones I have seen had a cranking handle....presumably cranked by the baddest child of the day.

[ebastler]

But are you suggesting that true modern craftsmen, construction workers, capenters, razor makers, leather workers, butchers, chefs, and tailors, all buy Tormeks and/or send their stuff out to professional sharpening services, now?

I'm not in any of these businesses, of course, but my guess is that what you describe is indeed the case: Craftsmen and workshops either buy a motor-driven grinding wheel (maybe not quite as high-end as the Tormek), or they use an external service. Small or one-man sharpening services are pretty common; some of them are mobile with all equipment installed in a little van, and they run regular routes or visit larger customers on demand.

[KL27x]

Craftsmen and workshops either buy a motor-driven grinding wheel

Yeah, I think they're super common. But play along, here. Specifically in the context of keeping an edge keen? Like when it get slightly dull, the tool is no good? But 20 seconds with a cheap, portable doodad would bring it back? The motor driven whatnot could not do this as fast, even?

90% of modern humans probably don't need to do this. To some of these people, this is maybe a foreign concept. That a power grinder, even a water wheel specifically made for super fine honing, is not necessarily convenient/improvement just because it can remove more material faster. On this kind of blades, the grinders are convenient only for occasional use for the rare regrind. At least to the person who has the ability to do this that other way.

[ebastler]

Well, for a quick touch-up of knives, these are very common in kitchens (commercial and at home) over here: https://de.wikipedia.org/wiki/Wetzstahl

Either steel or ceramic. I assume other businesses use them as well.

[tautech]

Those in trades that I know, more and more use power tools and most use tungsten cutting edges some of which are quite cheap today so the incentive to use tool or HSS steels and the sharpening skills required are such that the skills are slowly being lost. Even using ebastler's argument of using sharpening services is becoming less as the cost of many cutting tools diminish.
Time is money so if a tool edge is removed for sharpening it's now more efficient to fit a new one and then only the more expensive cutting edges get sent away for sharpening.
Many professions use outside sharpening services, some only to have their tools put 'back into shape' for them to then manage sharpness on a short term basis. Here butchers often use a service to keep their knives in good shape and just steel an edge on them whenever needed.
Even the carpenter doesn't use chisels or planes much now as most finishing items like doors are pre assembled and only require fitting to an opening whereas much assembly is done with routers today.

[KL27x]

You guys both make very good points.

Ebastler, yep. There are many ways to skin this cat. And some will be better for one person's needs than the other. Or maybe it's just a matter of what one knows or has been exposed to, and there's no need to change, because it works. I don't think it's weird that people have gone to other alternatives. I think it's weird that we think the way we use these arkansas stones today (if you believe the internet) was the way they were always used in the past. Because that isn't very useful, at least for a time/era when it was best thing going for a much more significant need. Esp when it is actually extremely good at this other need, even when compared to modern alternatives (IMO, of course), when used in this strange way which is pretty much seemingly unknown, today.

Tautech, yep. Saws are disposable. Bits are disposable. The only thing I can disagree is that fitting doors in wooden framed houses and wooden door frames is always going to require chisels rr bull nose planes, at least at some point to someone (ok maybe not the builder of a new house). But otherwise, I'd say you're right on the money.

[tautech]

The only thing I can disagree is that fitting doors in wooden framed houses and wooden door frames is always going to require chisels.

Nope, only for fitting the latches/locks and striker plates.
Doors are now almost always pre hung and their round corner hinges let in with a router.

Yeah, it’s not the fun it used to be ! 

[KL27x]

I kinda meant that at some point, some houses will warp and doors will stick. Or did we solve that with some kind of free-floating door frame?