Hi, Z. This might help (scroll down just a bit for grit comparison table):
Would anyone have an idea of the grit equivalents for the Sharpmaker's Medium, Fine, Ultra-fine stones in terms of waterstone grits with respect to how they refine and edge? A Sharpmaker medium stone is equivalent to what grit waterstone, etc. etc. Also, the same question for typical, run-of-the-mill smooth crock sticks ~= what waterstone grit.
You have to take the listing for the Spyderco stones with a grain of salt though. There is no "official" grit rating. The grit size is really the particle size (came from the grit through which the particles would fit through, so it was an upper bounds. These days, the techniques are much refined). The Spyderco stones all start with the same grit size, but they get processed differently. The stone get sintered. During the sintering process the particles fuse; they essentially melt, but not fully. They melt only at high points and in contact areas, leaving voids. If sintering it continued with sufficient flux and temperatures the particles continue to "deform" and the voids eventually fill (not completely but mostly) and the structure "smoothes out".
The gray stone are, AFAIK, open pore sintered, meaning the particles retain most of their structure, the whites are closed pore sintered, meaning most of the voids have been filled, and the UF stones are sintered like the white ones but additionally tumbled, to further smooth the surface of the stone. So it is pretty clear that a real "grit rating" isn't really possible anymore. All you can do is compare the scratches left by the ceramic stones, to those left by traditional stones. But that of course depends on how hard you press, and what condition the stones is in, so the comparison is somewhat subjective and all you going to get is a ballpark figure. Some people will argue for example that their UF stones are finer than a 6000 grit waterstone.
Personally, I would rate the Spyderco stones very similar as in DoW link.
Hope that helps and gives some perspective.
Absolutely true. Unfortunately, the manufacturer does not specify polygonality, only grit size. So short of trying it out there is really no way of knowing what you are going to get. Traditional japanese waterstones have a flake-like particle structure and seem to be cutting fast and leave a fine scratch pattern. Diamond stones have a very low polygonality, yet are cutting very fast. This is probably due to high penetration. Also to be considered is how well they are embedded in the substrate (e.g. how much the grit rolls around). There has been a study of the optimal polygonality of the abrasive on soft material. The result was that bimodal polygons seem to be optimal (large lower polygonal structure with a smaller structure of higher polygonality on top). In general a statistical orientation has to be assumed (I have never heard of an oriented hone). A lower polygonality my present a larger cutting edge, but on average is more likely to present a non-cutting surface, so there is a statistical trade-off. A bimodal polygonality will present a large surface or edge which will always present cutting edges due to the smaller structure on top. However, all in all, this is a field that would benefit from a much more thorough investigation. AFAIK there hasn't been even a theoretical study of the optimal size of the larger and smaller structure or its polygonality. Alone the asignment of the polygonality is difficult, as the structure of the particle is not necessarily of specific crystalline shape as one might expect (and which is for example true for diamonds). It is also a property that is extremely difficult to control experimentally, so you can not simply run a series of increasing polygonality. If you want to be picky, you would also have to consider toughness of the particle as that will determine break-down. Actually, my first post on bladeforums was on polygonality, but as interesting this might be to some, I don't think it is much of relevance as, like I said, impossible to order a hone with a certain particle structure.
What HoB and dscheidt are saying is very evident when you use a variety of abrasives. With ceramic in particular, and also to a noticeable extent with aluminum oxide (India) stones, the quality of finish you get depends on how much pressure you use ... and my belief is that this, in turn, has to do with the particle shape.
With diamond hones, however, the finish isn't affected nearly so much by pressure, and to a lesser degree the same can be said of silicon carbide hones. IMO this is due to the relatively "sharper" crystalline qualities of these abrasives. So as HoB points out, the only thing that can really be compared when talking about grit of different abrasives like this is the distance between scratches left on the metal being worked. If we could examine those scratches under high magnification, we'd see wide variations in width vs. depth, and contour -- e.g a sharp "V" shaped scratch, or a more shallow, rounded "U" shape -- depending on the abrasive.
Actually, that is exactly what the study, that I was talking about, did, but it used a very soft material to abrade, because that way you get a maximum of crystalline and non crystalline structures that you can use for testing purposes (for steel, many of the structures would have been too soft). They precisely controlled pressure and precisely calculated from the scratch pattern under a microscope (SEM) the total volume of material removed in one pass. But particle breakdown for example was not an issue.
dscheidt is absolutely right: How would you define the size of a flake-like particle for example. I believe this is why we see some stones that leave a finer finish at 4000 grit than others at 8000 grit. But even with flake-like particles you have at least distinct particles. The ceramic stones present an even greater problem, as they don't consist of individual particles anymore. And they start out with the same particle size and yet gray, white and UF show a very distinctive finish.
WOW!!! Thanks for the new info. I never knew there was so much science behind fine scratching whether "U's" or V's". Please give me your crystalline guesstimate on this. If I sharpen a knife with waterstones (800, 4000, 6000), would any of the Spyderco Sharpmaker stones (Med., Fine, Ultra-fine) further refine the edge? I like to use the SS for quick and easy maintenance. Without knowing the juxtaposition of my various 'hedrons and how they survived sintering, would you take a polygonal crap shoot and give me your opinions? Again, the new info is much appreciated.
Last edited by Zeasor; 03-03-2008 at 10:59 AM.
I find there are practical implications in all this as well. For example I really don't care much for extra fine (1200 grit) diamond hones, because while the scratch pattern may be very fine, the scratches themselves are narrower, deeper and sharper than what you'll get with the same "effective grit" fine ceramic for example ... in fact just speaking subjectively I feel a medium grit ceramic gives a finer finished edge than does extra fine diamond. So IMO where diamond hones are most useful is at the coarser grits where fast removal is desired, and you'll be removing those deep, sharp scratches with other abrasives in the later stages of sharpening.
DoW, as usual, we think along the same lines. There should be a agreeingly nodding smily .
Longer answer: I am a big fan of the Sharpmaker and with increasingly light strokes on the flats you can get a very nicely polished edge, especially on the UF stones. Also due to the fact that alternating strokes are so easy and repeatable, I think you are able to get a very high quality edge on the Sharpmaker. But among the variety of japanese waterstones you will find some that will cut much faster and cleaner than the Sharpmaker, and which will leave a MUCH finer scratch pattern. A good 6000+ grit stone will leave IMHO a much finer scratch pattern. (Btw. I would never go 800, 4000, 6000. I believe on a knife edge you can afford to roughly triple the grit in each step: So 800-4000 is still ok but the gap is a bit on the large side, 4000-6000 is much too small a step, 4000-8000 I would consider minimum to notice obvious improvement, if a polished edge is desired). The available choice is IMHO the great advantage of the japanese stones, and waterstones is something that the japanese do REALLY well.
I started to write this really only to prepare you for a variety of estimated grits for the Sharpmaker. The question comes up very regularly and Spyderco always pointed out that it is not possible to give a "classical" grit rating. I have kept track of the "average" opinion of grit rating for the Spyderco stones on BF and the link that DoW gave early on in this thread represents that well and represents my personal opinion, too. To illustrate my point though, I would, personally rate the gray stones a bit rougher, as a pretty slow cutting 800 grit, instead of a 1000 grit as the link does. I agree on the assessment of the F and UF stones though (2500 and 4000#) respectively, but I really don't think it is worth to haggle about a couple hundred points. As I said, I will also vary from person to person, depending how much pressure the individual uses and how much build up is on the stones.
Your alternative for highly polished edges are strops with various compounds. The average CrO compound is 0.5 micron (compare with the table in DoW's link), and is graded very well (same with AlO powder (linde)). You can also get various diamond pastes anywhere from 0.01-10+ microns, which you can spread either directly on an MDF board or on leather covered MDF. Nozh has been using this with great success for quite some time.
Oops! I forgot to say THANKS one and all for making this a most helpful, informative forum.
Back atcha, HoB. I'm sure part of the reason we agree on so many things is that I've learned so much from your informative posts.Originally Posted by HoB
Yes, IMO that's what makes the Sharpmaker, and of course other ceramic "V" sharpeners, such great, practical tools. With very little effort or fuss you can achieve a high quality finished edge that strikes a very good balance between polish and toothiness for a wide range of cutting tasks. For such an easy device to use, the precision and efficiency with which you can apply or touch up a uniform, clean microbevel is unrivaled, IMO.I am a big fan of the Sharpmaker and with increasingly light strokes on the flats you can get a very nicely polished edge, especially on the UF stones. Also due to the fact that alternating strokes are so easy and repeatable, I think you are able to get a very high quality edge on the Sharpmaker.
I use Spyderco benchstones and Shapton Glasstones for anything finer than 600 grit. For high carbide stainless short of ZDP-189 (and even on ZDP on a good day), I get very good results with the Spyderco ceramics, to the point where I don't feel it is worth the hassle of pulling out the Shaptons and flattening them. Recently I have gotten a couple edges with the Spyderco Medium that whittle hair, which for me is very good, whereas I have trouble doing that on the 1000 grit Shapton (though I have less practice on it). The 2K Shapton finish seems similar to the Spyderco fine in sharpness (but shinier), and the Spyderco Ultra Fine comes out similar to my 8K Shapton as far as sharpness (sometimes sharper, sometimes not), though again the Shapton is shinier. Where the waterstones come into their own is in fast, clean cutting and leaving a mirror finish. I mainly use my Spyderco stones for microbevelling, so speed of cutting and stone loading isn't an issue there. But when I am cutting in a whole new bevel there is no question I would use the Shaptons after I used coarse diamonds or my 500 grit Bester waterstone to polish out the bevel. Also, on ZDP 189 and steels like Aogami Super Blue at 64 RC and M2 at 65 RC the Shaptons do a much better job at cutting cleaner edges on the knives, as the ceramics start to give me burr issues with those steels, and when you sharpen the whole bevel they tend to load up quickly. Also, in general, the waterstone will be far more forgiving as far as not forming unwanted burrs on any steel, though they are softer than ceramics and can be gouged if you aren't careful when trying to apply a microbevel.
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