I have a sharpening question ....

[Patrick Chase]

Oh groan .. another bloody sharpening thread. Well, perhaps this has a more practical goal.

Isn't that what everybody claims when they start one of these? Denial isn't just a river in Egypt and all that :-).

Fred asked a question (in another thread - I did not wish to sidetrack that) regarding the grit of the Shapton diamond dressing plate (which is 275 as I recall. I have one). What this reminded me of was a question I have been meaning to ask for some time regarding the grit of a dressing plate.

The Shapton is spec'ed based on a range. 45-54 micron particle size, 270-325 grit. If you do the math both micron/grit pairs are consistent with Shapton's usual (and inflated) 15 um = #1000 rating scheme. Call it #200 for real :-).

First off, we use stones (water-, iron- and diamond) of a range of grits to hone plane and chisel blades, usually starting around 1000 and ending north of 8000. Sometimes up to 50K. In waterstones I have Shapton 1000, Sigma 6000 and 13000. I am not sure what the Spyderco ceremanic stones are rated at. It does not matter.

The issue is 'what does it matter what grit we use to dress a stone?'. Does it make a difference to the results from (say) a polishing stone (8000 or 13000 grit) if the dressing stone is 275 grit or 600 grit? In other words, can the structure of a sharpening stone be altered by the grit of a dressing stone?

I think that the kind of stone and specifically the hardness/friability of the binder matters a lot here. As an extreme example, a diamond plate with a rough surface finish (as opposed to an *interrupted* surface as in DuoSharp and Atoma) will leave deep scratches, period. On the other extreme a slightly rough texture on a soft fine-grit waterstone will typically be smoothed down within the first few strokes.

Arks (and ceramics) are more like a diamond plate - if you ever use a Dan's translucent stone in "out of the box" condition (smooth lapped surface) and then flatten it with a coarse diamond plate you'll see a significant difference in effective grit that lasts a fair while.

Is this the same as using a stone which has grooves - would it make any difference whether the stone is smooth or pockmarked? Logic says to me that grit is grit, and that surface conditions do not matter.

See above. If the binder is hard enough then "clumps" of grits act like individual larger grits from a scratching perspective. That's the entire operating principle behind polycrystalline diamond (as used on your EZE-lap plates) and seeded-gel grits like Norzon. Both create coarse abrasives from tightly bonded "clumps" of smaller particles in a very hard binder. For waterstones what you say is basically true IMO.

However, I am reminded that the Tormek has a wheel that is 220 grit. It can be "regraded" to 1000 by using a dressing stone. No doubt this works so by a crushing action on the surface of the wheel, which reduces the 220 to 1000 particle size. Yes, no? But is this the same thing as a diamond dressing stone being run across the surface. Surely it is not crushing the grit. It may create larger or smaller mini "furrows" but these should not alter the grit, per se.

Different abrasives break down in different ways. Si-Carbide is super-hard but brittle, so it breaks down by sharding as you describe. Al-Oxide and Si-Oxide are softer but much tougher, so they break down by dulling. When a plate with monocrystalline diamonds dulls or when an Al-Oxide wheel or Ark "glazes", the points of the top layer of particles have been dulled to where they don't stick out as far from the surface (though note that this can only happen with a hard binder). The as-shipped Tormek wheel is Al-Oxide in a medium-hard binder, so you're basically glazing the surface there.

A second, related question ...

I read of warnings that dressing a polishing stone (e.g. Spyderco Ultra Fine, or a natural oilstone, such as a Hard Black Arkansas) will release fresher grit, and the stone will not polish as well as beforehand. To me, that is like saying the constant pressure of sharpening a blade crushes the grip, creating finer grit. However, the stone cannot remain this way since the surface becomes glazed and will not cut.

Spyderco and Arks both have very hard binders, so for those specific stones I think that's a true statement - they don't polish as well after lapping with a coarse stone. Note that glazed stones never truly stop cutting, they just get slower.

What is better, a dedicated stone for a specific task that is dressed frequently for ultimate cutting action, or one that works at a higher grit than intended by nature, but do so slowly? If the latter was supported (I shudder!), then we would all have a series of dressing plates ranging from 275 through 6000+ grit just to avoid hampering the potential of the polishing stone.

I'm very much in the "a dedicated stone for each purpose" camp (to admit otherwise would after all be an acknowledgement that my stone-whore-iness is pointless :-), but I think there's a lot of subjective preference here. I also use mostly waterstones, and find that #140 and #400 diamond plates are sufficient for all but the very coarsest stones (which get SiC grit). In the one recent instance where I flattened a translucent Ark I finished with #600 SiC powder, and lapped long enough to break the SiC down a bit (see above - SiC shards). I got a very smooth surface similar to Dan's.

[Patrick Chase]

Just information - Im not sure how to interpret it yet, but with luck this thread will help. ...... For the Shaptons, their web site (shapton-usa) says their lapping plate is for flattening Shapton stones from 500 grit to 30000 grit. They also say not to use it on water stones coarser than 1000 grit if they are made by other companies, but dont say why.

Maybe because coarse stones can be very hard on diamond plates and they just want to play safe.

All diamond plates are susceptible to diamonds falling out due to debonding. The Shapton lapping plate is particularly vulnerable because it uses resin-bonded diamonds, rather than being electroplated as with most plates. That's why they're able to hold a much tighter flatness spec (0.2 mils, 5 microns) than DMT or even Atoma. Coarse stones would denude that plate in fairly short order.

That's also why they say not to use it directly on metal blades.

[Warren Mickley]

I read of warnings that dressing a polishing stone (e.g. Spyderco Ultra Fine, or a natural oilstone, such as a Hard Black Arkansas) will release fresher grit, and the stone will not polish as well as beforehand. To me, that is like saying the constant pressure of sharpening a blade crushes the grip, creating finer grit. However, the stone cannot remain this way since the surface becomes glazed and will not cut. What is better, a dedicated stone for a specific task that is dressed frequently for ultimate cutting action, or one that works at a higher grit than intended by nature, but do so slowly? If the latter was supported (I shudder!), then we would all have a series of dressing plates ranging from 275 through 6000+ grit just to avoid hampering the potential of the polishing stone.

Abrading an Arkansas stone will scratch the stone. It will not "release" grit. A stone so abraded will temporarily act like a coarser stone.

There are several conditions which have been called "glazing". One is where the stone becomes loaded with steel particles. This is a danger when there is no oil or when the oil is too thin to suspend the particles. Oil stones are called such because a thick liquid is needed to keep the stone clean. If one uses a thin volatile liquid like Wd-40 or mineral spirits, he might as well use water. Another problem arises when an oil is used that is not very refined. The volatile portion of the oil evaporates, leaving a residue which is gummy or worse and also tends to foul the stone.

For a stone like sandstone, if the binder is too hard or there is not enough pressure, the stone can become smooth and cut slowly which is a problem with this type of stone. However with Arkansas stones, we are not trying to remove material as much as smooth the surface. We use the stones in the smooth condition. They do their work well, which is why we have used oil stones for millennia. They do take skill and experience.

A "higher grit than intended by nature"? Is this some kind of religious statement? Working with natural stones is different than working with some man made stone where we read the manufacturers instructions and recommendations. Sharpening with Arkansas stones is an art. A fine Arkansas stone that is not abused will not need dressing over a lifetime of full time work.

[Ray Bohn]

Thanks for starting this thread topic. As a fairly new hand woodworker, I have noticed something related to this topic but felt insecure in bring it up.

I use a Atoma 400 for flattening my 1000, 3000, and 8000 Japanese waterstones. The 1000 and 3000 stones end up clean with no scratch pattern, but the 8000 looks horrible when I start using it. The swarf fills up the scratches.

From the opinions posted here, it appears that I could use a finer diamond stone on my 8000 water stone , but it probably doesn't matter that much when it come to creating an edge, but may shorten the life of the water stone.

Am I understanding this conversation correctly?

Thanks

[Luke Dupont]

Thanks for starting this thread topic. As a fairly new hand woodworker, I have noticed something related to this topic but felt insecure in bring it up.

I use a Atoma 400 for flattening my 1000, 3000, and 8000 Japanese waterstones. The 1000 and 3000 stones end up clean with no scratch pattern, but the 8000 looks horrible when I start using it. The swarf fills up the scratches.

From the opinions posted here, it appears that I could use a finer diamond stone on my 8000 water stone , but it probably doesn't matter that much when it come to creating an edge, but may shorten the life of the water stone.

Am I understanding this conversation correctly?

Thanks

That's probably accurate. I don't have as much experience with waterstones, so someone can probably comment better, but from what I understand Atoma plates are very coarse/aggressive, so they will remove a lot of material and may even affect the finish on your 8000 stone *if* you don't spend long enough on it to wear down past the deep gouges that it makes.

If you want to test whether or not it's affecting the edge that you get, you could flatten it, and then wear it in with the back of your chisel before sharpening; or, alternatively, flatten it with something a little finer like sandpaper.

All in all, the best way to figure these things out is to experiment yourself.

[Derek Cohen]

Abrading an Arkansas stone will scratch the stone. It will not "release" grit. A stone so abraded will temporarily act like a coarser stone.

Warren, that is what puzzles me. My logic says that, if coarser grit is not released and the grit remains the same, then why should it matter whether the surface is furrowed or scratched?

To use another analogy, if the stone was a wooden board that required flattening, there should be no difference in wear when cutting the hills and the valleys.

There are several conditions which have been called "glazing". One is where the stone becomes loaded with steel particles. This is a danger when there is no oil or when the oil is too thin to suspend the particles. Oil stones are called such because a thick liquid is needed to keep the stone clean. If one uses a thin volatile liquid like Wd-40 or mineral spirits, he might as well use water ..

This is what I was referring to. For example, the manufacturer states that a Sypderco (manmade) can be used dry. This does not made sense to me since all sharpening media needs to carry away swarf, or otherwise the stone will glaze on the surface. I use soapy water on mine, as I would on a Shapton waterstone (also manmade). I added the question about the Arkansas because it is natural, not manmade. I have minimal knowledge of oilstones (other than the Arkansas I use in the kitchen), but recall a video of Larry Williams dressing his stones with a diamond stone, and recommending that this be done frequently. It raised the question whether this alters the grit, and if so how it does this.

For a stone like sandstone, if the binder is too hard or there is not enough pressure, the stone can become smooth and cut slowly which is a problem with this type of stone. However with Arkansas stones, we are not trying to remove material as much as smooth the surface. We use the stones in the smooth condition. They do their work well, which is why we have used oil stones for millennia. They do take skill and experience.

Ceramic stones, such as Spyderco, have a very hard binder. Witness the many who have worn out diamond stones flattening their new Spyderco. In maintaining these stones, are we simply smoothing the surface or releasing fresh grit? Will I expect an Ultra Fine Spyderco (perhaps 8000 grit) to now cut more like a Medium Spyderco (perhaps 3000 grit)?

Another analogy: I am also reminded of what happens when one uses diamond paste on a cast iron lap - the diamond will bed, and it is what lies above the surface that does the abrading. Now if one used the same paste on a strip of leather, some of the diamonds might sit on the surface, but most will end up being pushed below. A smooth surface, by definition, does not abrade.

Regards from Perth

Derek

[James Pallas]

I'm a bit skeptical about getting into a sharpening thread. I guess I'm just interested in the conclusions. The question I have is this: Why not find out what the providers of the stones use to grade, lap or whatever it may be called and just try to emulate that as close as possible? Would that not make the stone close to what it was when freshly done? It seems that there is some break in time for new stones but they stay flat a long time if properly used. Let me finish by saying I started out using oil stones and still have some but have moved on and I'm happy with my set up now. I'm just interested in learning just in case I would want to use oil stones again.
Jim

[Warren Mickley]

Warren, that is what puzzles me. My logic says that, if coarser grit is not released and the grit remains the same, then why should it matter whether the surface is furrowed or scratched?

Arkansas stones are partly metamorphosed so that the crystals are sort of melted together. There is no binder. I think you will remain puzzled as long as you view an Arkansas stone as some sort of water stone.

[Luke Dupont]

Warren, that is what puzzles me. My logic says that, if coarser grit is not released and the grit remains the same, then why should it matter whether the surface is furrowed or scratched?

To use another analogy, if the stone was a wooden board that required flattening, there should be no difference in wear when cutting the hills and the valleys.

I'm not sure I follow your logic.

Dressing an Arkansas with a diamond plate drastically alters perceived "grit" (note: "grit" is a misleading way to think about natural stones, though) because it changes the shape of the surface. Natural stones are very different than man-made ones, and grit does not really apply to them.

Manmade stones have a sharper, more granular structure to their surface, whereas natural stones have a much smoother surface with less variation in the depth of the valleys and height of the hills, if you will, and the "hills" are much more rounded.

Hrm... Okay, let's try some text art to illustrate the difference.

Assuming these surfaces to be of the same "grit" (which, I will incorrectly define as the spacing between the particles or "peaks" doing the cutting, since we're kind of comparing apples and oranges here) which will leave a rougher surface, and which will leave a smoother one?

Surface A:
/\/\/\/\/\/\/\/\/\

Surface B:
oOoOoOoOoOoOo

Now, if I abrade surface B with surface A, can I not expect surface B to take on a similar geometry as surface A, seeing as I am cutting deeper, more jagged ridges into what was once a smoother, rounder surface with shallower ridges?

This is what happens when you abrade a natural stone with a diamond stone. It changes the shape of the surface itself. And, unlike a waterstone, it can stay this way for a while because it's solid stone; it doesn't abrade away quickly and release its grit/particles. There is no grit/there are no particles, and there is no binding. It's just the shape of a mostly continuous, solid surface of the stone that dictates how it cuts. I mean, that is something of an over simplification; there is of course inherent structure to stone and it will break down in a particular way, but it's a little different from how particles bonded together with an abrasive work.

[James Waldron]

I have medium and ultra-fine Spyderco stones. Unlike the experience of others, both came in quite flat.

With considerable doubts, I have so far used them dry. And, so far, they both cut very well. And, following the company line, I wash them periodically with a powdered kitchen cleanser. The one I use is a non-abrasive, oxalic acid based cleanser (Bar Keeper's Friend). Works a charm, and has so far dispelled my doubts about dry sharpening and polishing.

The UF stone turns a burr quickly without starting on the coarser stone many times, usually 15-20 sharpenings, so it gets most of the usage. (I remove the burr with green compound on mdf in a few passes and get back to my project.) So far, when it's clean, my eye can't tell it's been used at all. It looks to my eyes -- which are not young, but still pretty decent -- just as it did when new. My edges can't tell it's not new either. My medium has so much less use it may not be timely to evaluate it's durability, but so far, it still performs like new. It gets washed far less often than the UF. It has thus far remained quite flat.

My use isn't all that long term yet, but so far it has been the most convenient, the most rapid, the cleanest sharpening approach I have ever used and my edges are as sharp as any I have ever been able to attain. I'm not going back to my diamonds, my Arks, or any of the other possibilities our there. Maybe we can all look forward to someone making really fine grit CBN stones one of these days, and they may be better than the ceramics, but until then, I'm sticking with my Spyderco.

[Patrick Chase]

Thanks for starting this thread topic. As a fairly new hand woodworker, I have noticed something related to this topic but felt insecure in bring it up.

I use a Atoma 400 for flattening my 1000, 3000, and 8000 Japanese waterstones. The 1000 and 3000 stones end up clean with no scratch pattern, but the 8000 looks horrible when I start using it. The swarf fills up the scratches.

From the opinions posted here, it appears that I could use a finer diamond stone on my 8000 water stone , but it probably doesn't matter that much when it come to creating an edge, but may shorten the life of the water stone.

Am I understanding this conversation correctly?

Thanks

I think the key is to judge the stone by its results, not by its appearance. The fact that the surface of the stone looks rough doesn't matter if it leaves a smooth finish on your tools when used the way you use it. #400 corresponds to ~1.2 mil (30 micron) particle size, so you're not losing much life to the resulting scratch pattern as long as you don't flatten compulsively.

[Patrick Chase]

It changes the shape of the surface itself. And, unlike a waterstone, it can stay this way for a while because it's solid stone; it doesn't abrade away quickly and release its grit/particles. There is no grit/there are no particles, and there is no binding.

This is about as wrong as it could possibly be. Arks have grain structure, meaning that individual crystalline SiO4 (quartz) particles are bound into a larger whole. The size of those grains is exactly what differentiates soft/coarse stones from hard/fine ones.

If Arks didn't have grain structure then they would be jewelry, and would be completely unsuitable for honing because the surfaces of individual quartz crystals are smooth.

Also it's well known that interrupted surfaces from furrows, scratches, holes, etc don't significantly impact finish. That's why DMT DuoSharp and Atoma plates work. Small (low multiple of the grain/particle size) high points are what cause trouble.