To me, that sounds too good to be true.
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Norton Ascent CA Single Grit Benchstone
- Thread starter Mr.Wizard
- Start date
It is. Everything wears, even diamond. The "never needs lapping" may well be true - for a guy that only uses the hone once or twice a year for light finishing; but it's not because the hone won't ever wear. This is marketing fluff.
And you know damn well that Norton will argue over what "needs lapping" actually means anyway if you were to try a warranty claim. I'm sure their interpretation would be: "Does the hone still abrade metal? Doesn't need lapping."
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They'd try to claim it means it doesn't need flattening, rather than meaning that it never benefits from refreshing the surface.
Extra clean (pure) Aluminum Oxide is not as hard as Vanadium Carbide. Why would I expect to avoid hard Carbide tear out when using an Ascent stone on an S-125-V blade. They make this stone in a size (11 1/2 X 2 1/2 X 1/2”) that fits the large oil bath Trihone, but do not recommend using oil.
My Shapton Glass stones are a high grade Al2O3, but they need occasional flattening. How does the Ascent formulation differ from the Shapton one?
My Shapton Glass stones are a high grade Al2O3, but they need occasional flattening. How does the Ascent formulation differ from the Shapton one?
It is a fully sintered/fused hone composed almost entirely of aluminum oxide. Your Shapton hones are a percentage of aluminum oxide (some Shapton hones also have silicon carbide) and a percentage of a resin (what basically amounts to glue or epoxy) binder pressed together in a mold.
Neither Aluminum Oxide nor Silicon Carbide are as hard as Vanadium Carbide, Titanium Carbide, or Niobium Carbide. My CPM knives contain 1 & 3. My Titanium knives have #2. Increasing the purity and/or concentration of Al2O3 does not improve hardness. Aluminum Oxide struggles with Tungsten Carbide which is softer than the 3 aforementioned Carbides.
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Sintering is essentially like synthetic sedimentary stone. Rather than being held together by a binder, the grains are subjected to such enormous heat and pressure that they fuse together. Resin or vitrified bond stones mostly wear not due to the grains themselves fracturing, but from the binder yielding to pressure and allowing the grains to dislodge. In the case of sintered stones the bond of the fused grains is so hard that it will not shed grit under normal conditions.
Also carbide tearout is something that's been found not to really occur under the overwhelming majority of circumstances, but you COULD expect the aluminum oxide to fail to abrade the vanadium carbides at the apex of the edge, merely burnishing them instead, and the carbides would cause wear to the surface grains of aluminum oxide, leading to further burnishing of any knives used on it. You'd end up with rubbing instead of cutting, effectively having glazed the stone. A surface dressing with diamond or CBN (lapidary grit on a flat piece of glass or granite tile would be better than a diamond plate) would be necessary to restore proper cutting action. Sintered stones work less like sandpaper and more like a file. The cut of the surface affects the speed and finish of the workpiece more than the size of the specific abrasive grains are.
Also carbide tearout is something that's been found not to really occur under the overwhelming majority of circumstances, but you COULD expect the aluminum oxide to fail to abrade the vanadium carbides at the apex of the edge, merely burnishing them instead, and the carbides would cause wear to the surface grains of aluminum oxide, leading to further burnishing of any knives used on it. You'd end up with rubbing instead of cutting, effectively having glazed the stone. A surface dressing with diamond or CBN (lapidary grit on a flat piece of glass or granite tile would be better than a diamond plate) would be necessary to restore proper cutting action. Sintered stones work less like sandpaper and more like a file. The cut of the surface affects the speed and finish of the workpiece more than the size of the specific abrasive grains are.
Nobody was claiming that aluminum oxide is harder than carbides, not sure why you're going down that road. The fused hones are bound together in what is effectively a much harder bond than a resin bond hone like a Shapton - of course the actual Aluminum Oxide abrasive isn't any harder than in any other hone that contains it. As 42 noted, the hone effectively becomes one solid piece after sintering/fusing. The many particles of aluminum oxide are effectively joined as solidly as though they were melted together.
I believe that it's pretty common knowledge these days that if you want to effectively move much steel on a blade containing the harder carbides that a CBN or diamond hone should be used. Anything less is not nearly as effective for much more than light finishing work.
Neither do I... Don't think anyone here has claimed that it would. I tried a Chosera 1k to set a bevel on a T15 HSS blade I made once. Didn't try for long, nor more than once. I know when I'm wasting my time... This Norton fused hone might do okay for final finish honing on some of those blade steels with a microbevel, but not much else IMO. And BTW these can be made to finish much finer than 1200 grit equivalent with the proper surface prep.
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When used with hard carbide-rich steels, I view the usefulness of an AlOx ceramic in very narrow and specific terms. If using it at all on such steels, I ONLY use it for what I call 'cleaning up the edge' after sharpening on diamond. Termed as such, it just means I'm viewing it as doing some very, very minimal refinement of the edge portions NOT containing the carbides themselves, as well as knocking off any loose remnants left weakened by the sharpening process. I don't like the loss of bite that tends to occur on carbide-heavy steels if I take it any further than that, on the ceramic. So, I use it as minimally as possible. If I do it right, in that respect, it does enhance sharpness on the edge, by removing the weak bits and refining the portions it can handle. But I don't delude myself into believing that it's capable of doing anything and everything on such steels - it has its limitations. If one knows what those limitations are and works within them with some finesse, it's still possible to find the tool useful on steels that might otherwise be assumed as too much for it to handle.
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High vanadium steels are usually best suited to cutting abrasive materials, which usually are easiest to cut using slicing cuts. Slicing cuts work better with edges produced in the lower grit ranges where aluminum oxide is still an effective abrasive anyhow.
All told this sounds like a stone you'd personally get very little use from. And that's okay.
All told this sounds like a stone you'd personally get very little use from. And that's okay.