Really confused about grit size.

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Aug 3, 2019
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I've looked on Japanese whetstones and the recommendations seem to be to use a 1000 grit for ordinary sharpening and go down a bit below that only when the edge is badly damaged or needs reprofiling. However the Lansky basic ceramic guided system has stones with grits 120, 280, 600. That would be considered very coarse by the whetstone standards. I read that if you wanted a touch up often you could use a 3000 grit stone not to wear to much on the blade. Very confusing.
 
Yes Sir, grit ratings are one of the most confusing things about sharpening. Part of this is because there are multiple rating systems that all use similar numbers, but the numbers mean different things in terms of coarseness. Examples are JIS, FEPA, and ANSI. Look at the grand unified grit chart in the stickies section and you'll find a giant conversion table so you can compare them.

But the real part that's confusing is abrasive materials science. Different substances cut differently. For example, waterstones are generally make from aluminum oxide, which is friable. That funny word means that the abrasive breaks down as you use it. The points of the abrasive particles break off and expose more fresh abrasive below them. But... waterstones are used with water, so a slurry is formed by these broken down particles. This tends to produce a finer finish than you would expect, because the slurry, lubricated by water, contains finer abrasives (broken down) then the stone itself. The combination of these factors makes the waterstone finish different than any other. It cuts kinda fast, yet produces a finish that's finer than you might expect.

Contrast this with diamond abrasives. Diamonds do not break down. There is no slurry. Even more importantly, diamonds have a very pointy shape which makes them "sharp". They are so hard and so sharp (compared to other abrasives), that they dig into steel much deeper than you might expect. So a "320 grit" diamond plate will tend to produce a more coarse finish than an aluminum oxide 320 grit stone or belt.

What abrasive to use for what task becomes a matter of experience. A lot of people with expensive, shiny, and "finely made" blades tend to be very scared of "destroying the blade" with an abrasive that's too coarse. In my own experience, I often use abrasives in the 60 to 120 micron range (about 320 grit to 100 grit). Blades that are very dull need a lot of abrasion. Blades that are nearly sharp don't need very much. It's very much a matter of the right tool for the right job.

I'll stop here and hope that this has helped some.

Brian.
 
I should add that Japanese knife owners and maintainers tend to be much more conservative than a lot of the knife world. I would tend to discount the advice that you paraphrased above unless you are working on Japanese knives and using waterstones.

Brian.
 
So then I think I should rely on Lansky's recommendation rather than read and compare grit with Japanese waterstones, since that seems to be not really comparable in that way?
 
Diamond is fragile. They can break, shear off like glass. Then you are rubbing a blade on small grains of diamond. I have seen this occur, with a new diamond stone. Thats how they get worn down. DM
I remember my first pouch of 250-micron monocrystalline diamond powder. I was so tired of SiC powder consumption in stone flattening. I wanted INDESTRUCTIBLE grain! I was so naive to believe in fairy tales.
Piece of glass.
Diamond powder for $10.
Water.
8" Translucent Arkansas.
After 10 seconds: WTF where are my diamonds?
 
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Lansky would be using the FEPA scale while Japanese water stones are generally along the JIS.
The judgment part is important, I use a 500 (JIS) when I want to apex, but the bevels are good. But I (believe) I have an idea of when to stop too.
But if I had to set a new bevel or a knife is dull, the 220 comes out.
You stop and check often so you know when you get to where you want without taking out too much material.

Yeah, if a knife cuts but needs more tooth or isn't quite sharp a 1000 will do fine.
 
Lansky would be using the FEPA scale while Japanese water stones are generally along the JIS.
The judgment part is important, I use a 500 (JIS) when I want to apex, but the bevels are good. But I (believe) I have an idea of when to stop too.
But if I had to set a new bevel or a knife is dull, the 220 comes out.
You stop and check often so you know when you get to where you want without taking out too much material.

Yeah, if a knife cuts but needs more tooth or isn't quite sharp a 1000 will do fine.
Yes but I found Fepa-f and Fepa-p,. Which one? In the stickies section.
 
Diamond is fragile. They can break, shear off like glass. Then you are rubbing a blade on small grains of diamond. I have seen this occur, with a new diamond stone. Thats how they get worn down. DM
Depends on the diamond. Like other abrasives it comes in different properties, some tough, some hard, some friable, some cheap junk. Keep in mind that the plated diamond stones are on the low end of what can be achieved.
 
Yes but I found Fepa-f and Fepa-p,. Which one? In the stickies section.

FEPA-P applies only to grit used in sandpaper. FEPA-F applies to grit used in stones or sharpening wheels. So, between those two, FEPA-F might more closely apply to Lansky's stones. Another thing, the FEPA standards are European standards applied to grit manufactured in Europe. Lansky, being an American company, might be grading to an ANSI/CAMI standard (USA).

That being said, I don't think Lansky has ever published which recognized standard their stones are compared to, if any. That happens a lot, actually, as many manufacturers apply their own scale in assigning 'grit' values to their own products. This is just one part in many, of why it's usually so difficult to directly and accurately compare different types or brands of abrasive products with one another.
 
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This ^ was a new DMT dia x- coarse. I was using it to thin the convex grind to a V grind. On a 9" carving blade of 440c. A lot of material came off. DM
 
Diamond abrasives seem to wear down quickly against softer steels. So my theory is that the binder is what's breaking down most of the time as more ductile materials can easily reach past the abrasives and wear against whatever is holding the diamonds.
This could also partly explain why coarser grits can wear down even faster since there's more space between the diamonds. A 'bed of nails' sort of effect maybe.
 
The diamonds shouldn’t wear down on soft steels, but I could see the stone getting clogged with metal between the stones. It would need to be cleaned more often.
 
I don't like diamonds with soft steel. It seems to plough trenches, pushing the steel to the side instead of removing chips. And while the diamond crystals don't really wear they do dig into the steel too deep which can overload either the crystal, snapping it in half, or the bond adhesion, pulling it out. Diamond is incredibly hard to bond to, especially with metal.

As for trying to compare stones on paper that is kind of impossible, even if you are familiar with the characteristics of the different abrasives and grits. What the paper doesn't say is the bond, which has about as much affect on the stone as the abrasive, and there are much deeper differences than vitreous, resin, or metal. You really just need to try them out to understand the differences.
 
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Wet/Dry sandpaper comes in various grits, I discovered this rarity and found it to be quite abrasive and actually difficult to use...

1 Grit sandpaper by GaryWGraley, on Flickr

G2
(just kidding of course...)
 
the Lansky basic ceramic guided system has stones with grits 120, 280, 600. That would be considered very coarse by the whetstone standards. I read that if you wanted a touch up often you could use a 3000 grit stone not to wear to much on the blade.

Don't overthink this. With where you are and what you're trying to do, trying to figure out differences in grit sizes is not going to help.

Focus on the blade and what you're trying to achieve. After a little bit of use, unless you're cutting only jello and pudding, the edge is going to get banged up and worn. There's no way you'll want to start with a 3000... regardless of by what standard you're measuring grit. I don't let my knives get dull or severely damaged, and I'll typically start with a stone between 250 and 650, depending on a lot of things, including my mood. If your edge isn't misused, you're not taking off a lot of material, regardless of with what grit size you start.
 
OP: I understand what you're saying. All this talk about grit conversions and whatever else is besides the point.

You're saying that modern sharpening theory calls for a coarse stone, (200-400 grit) as your first stone, for typical sharpening of dull knives, whereas Japanese waterstone theory calls for a 1k stone as your first stone to sharpen a dull knife.

JIS and American grit ratings are not all that different. This discrepancy in coarest starting stone is more a difference in philosophy. Abrasive type will make a difference, but generally speaking I think 1k stones aren't given enough credit for their ability to remove material.

The difference between a 1k stone and a 300 grit stone is more than just abrasive size. The thing about using a smaller abrasive is you can pack more abrasives into the same amount of space. So with a 300 grit stone you have fewer, larger abrasives plowing through metal, making fewer but larger cuts, versus a 1k stone having a larger quantity of smaller abrasives making more, but smaller cuts into the metal. Which one removes material faster? It's not an obvious answer.

I think a 1k stone can do a lot of jobs most people currently use a 300 grit stone for, while leaving a finer edge and more polished bevels.
 
If you really want to go mad try to figure out cartridge caliber designations on ammunition.
 
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