Some stainless knives are hard to sharpen well

I sharpen knives on my bench grinder. I have a relatively fine hard wheel on one end and a polishing style non-vowen wheel on the other.
Most stainless kitchen knives that are of whitish color are relatively easy to sharpen and then cut well.
I noticed that some knives with greyer stainless steel blades are difficult to sharpen and somehow they do not like to stay sharp.
I spent a while today sharpening those two grey knives, first cutting a sharp vee on the grinding wheel, and then polishing, it finally seems acceptable. But somehow they are clearly worse than other knives. What gives? Ayn idea what steels they are?
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On 9/22/2019 8:42 PM, Ignoramus9254 wrote:

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Yes they are but so are the others
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See if a file cuts the steel, at the duller part by the handle.
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On Sep 22, 2019, Ignoramus9254 wrote

powerful for the purpose, and almost certain to burn the steel right at the former cutting edge. The grayer steel is probably also magnetic - as others have implied, this is most likely the good knife steel.
The brighter steel is suitable for butter knives.
Some photos would help.
There is a large literature on knife sharpening, but for cooking knives an india (red) stone used with water works well.
Joe Gwinn
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On Sunday, September 22, 2019 at 9:42:41 PM UTC-4, Ignoramus9254 wrote:

Hi Iggy! I don't have time to get much into this, but as Joe said, sharpeni ng good knives on a bench grinder is a good way to wreck them. (Joe -- real India stones (a Norton trademark for aluminum oxide) are yellow-brown, not red, unless Norton has licensed out the trademark to someone who makes the m red)
All stainless can be "bright," but it's the austenitic, 18-8 types (302, mo re or less) that won't hold an edge. However, if you sharpen them aggressiv ely -- like with a bench grinder -- they will *take* an edge, and a bench g rinder typically leaves a microscopic serration that gives the illusion of making the knife cut well. In vegetables, it really *does* cut well, for a while. And it's good for meat, too. In fact, that microscopic serration act ually improves performance for most *slicing* operations, but not for *chis eling* operations, where you push the edge into whatever you're cutting. Fo r that, you want ultrafine edges, and very sharp ones.
Good kitchen cutlery and quality pocket knives today are made from 400 Seri es (410, 440, 441) stainless. It is heat-treated and MUCH harder, and much harder to sharpen. (410 doesn't have much carbon, but it has enough mangane se and chromium to multiply the effect of the carbon in conversion to marte nsite upon heat treatment). But it holds a good edge. It is rough on alumin um oxide stones -- I only use them for finishing. For hard stainless, a sil icon carbide stone, which typically is blue-gray, is much better.
Hard wheels are the worst for heat build up and wrecking a good knife or ot her cutting edge. Soft ones, often white, are used commercially, and VERY c arefully to avoid drawing out the temper.
If you have a microscope, you can learn a lot by examining the edges after you sharpen them. You'll see that some stones will not produce a really fin e edge on hard stainless. The edge chips if you use too much pressure, and it doesn't do much at all if you use too little.
I learned a lot of this from Norton folks when I was writing about it, and from 60 years of screwing up good edges. d8-)
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On Tuesday, September 24, 2019 at 1:52:28 PM UTC-4, snipped-for-privacy@gmail.com wrot e:

ning good knives on a bench grinder is a good way to wreck them. (Joe -- re al India stones (a Norton trademark for aluminum oxide) are yellow-brown, n ot red, unless Norton has licensed out the trademark to someone who makes t hem red)

more or less) that won't hold an edge. However, if you sharpen them aggress ively -- like with a bench grinder -- they will *take* an edge, and a bench grinder typically leaves a microscopic serration that gives the illusion o f making the knife cut well. In vegetables, it really *does* cut well, for a while. And it's good for meat, too. In fact, that microscopic serration a ctually improves performance for most *slicing* operations, but not for *ch iseling* operations, where you push the edge into whatever you're cutting. For that, you want ultrafine edges, and very sharp ones.

ries (410, 440, 441) stainless. It is heat-treated and MUCH harder, and muc h harder to sharpen. (410 doesn't have much carbon, but it has enough manga nese and chromium to multiply the effect of the carbon in conversion to mar tensite upon heat treatment). But it holds a good edge. It is rough on alum inum oxide stones -- I only use them for finishing. For hard stainless, a s ilicon carbide stone, which typically is blue-gray, is much better.

other cutting edge. Soft ones, often white, are used commercially, and VERY carefully to avoid drawing out the temper.

r you sharpen them. You'll see that some stones will not produce a really f ine edge on hard stainless. The edge chips if you use too much pressure, an d it doesn't do much at all if you use too little.

d from 60 years of screwing up good edges. d8-)

Whoops, I said "blue-gray" for SiC. Good ones often are green.
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On Sunday, September 22, 2019 at 9:42:41 PM UTC-4, Ignoramus9254 wrote:

Hi Iggy! I don't have time to get much into this, but as Joe said, sharpening good knives on a bench grinder is a good way to wreck them. (Joe -- real India stones (a Norton trademark for aluminum oxide) are yellow-brown, not red, unless Norton has licensed out the trademark to someone who makes them red) ...
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On Tuesday, September 24, 2019 at 4:39:56 PM UTC-4, Jim Wilkins wrote:

Well, Norton has made "India" stones for a very long time. One of my India bench stones dates to the late '40s. Another, early '50s. And I have severa l small stones, plus about a half-dozen India slips. They're all the same c olor, but they may have changed it since then.
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On Tuesday, September 24, 2019 at 4:39:56 PM UTC-4, Jim Wilkins wrote:

Well, Norton has made "India" stones for a very long time. One of my India bench stones dates to the late '40s. Another, early '50s. And I have several small stones, plus about a half-dozen India slips. They're all the same color, but they may have changed it since then.
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