Thread: Grits

I saw this post at knifeforums and thought some of you could use this information. The poster (yuzuha) is a well regarded sharpener. She frequently posts detailed information about various stones and their characteristics.

"According to the table in Norton's catalog their waterstones correspond to the following micron sizes:
220 grit = 65 microns
1,000 grit = 14 microns (this is 800 grit Japanese industrial standard)
4,000 grit = 6 microns (about 2,300 grit JIS)
8,000 grit = 3 microns (4,000 grit JIS)

For the grit sizes of imported Japanese stones look at the first two columns here: http://members.cox.net/~yuzuha/jisgrits.html
(this is the more recent Japanese industrial standard that uses electrical resistance to sort grit... the older standard used a sedimentation method and the numbers were slightly coarser for a given grit number... i.e. the old grit number 3,000 was 5.7 microns and the closest in the new grit table is 5.5 which is now 2,500 grit).

So, yes... Norton stones are considerably coarser than a Japanese stone with the same grit number. And, with more than one measurement method, two Japanese stones of the same grit might be different too but they should still be pretty close to each other.

Bear in mind that the cutting speed and surface finish produced are not only a function of the micron size of the abrasive grains but are also influenced by the binding material and how densely the grains are bonded together. I.e. two stones can use 5 micron abrasives... a porous soft bond will cut faster, a dense, tight bond will leave a finer finish. Then there are some stones with a slightly flexible resin binder that try to get the best of both worlds. Others, like the natural aoto/blue stone have grit that will break fairly easily... i.e. the stone itself is about 1,000 grit, but the grains come off the stone and form a sharpening paste... the grains in the paste then break between the stone and blade and become smaller, so you can get a 3,000 grit finish off a blue stone if you take advantage of the slurry."

Larry,

Very informative. However, based on the thread name, I thought we were going to discuss breakfast food!

RT

Originally Posted by rtaylor61

Larry,
Very informative. However, based on the thread name, I thought we were going to discuss breakfast food!
RT

Works every time.

Originally Posted by rtaylor61

Larry,

Very informative. However, based on the thread name, I thought we were going to discuss breakfast food!

RT

I too thought that this post should be in the 'Off Topic' under our recipies discussion .

KD, great post..thanks.
Ed

Thanks for posting that info!
However.... me smells a rat! It sounds like there is a game being played here buy the sellers of honing stones.
The Chinese created their own standard for grading so that their 12000 grit stone from Woodcraft is not the same as a 12,000 stone from anyone else.
The Japanese are credited with creating the standards for the higher grit ranges initially but now are going to change it because they have a different method of particle size grading?

Oh well.... it still boils down to the end result obtained. It may very well be that some of the Japanese and Chinese stone's are of a finer grit size but its what happens when the rubber meets the road that really counts.
I still have not had a japanese stone that cuts as fast as a Norton and some people will say that the Belgian coticule gives the finest edge. Maybe its because the 6 micron garnets in the Belgian fracture into smaller pieces and give a finer scratch pattern?

I have been intersted in this grit thing for several years now and frankly there are so many variables that its almost impossible to say that one is better than another. You just have to try some hones, learn how to use them and beware the latest and greatest thing.

I am being a bit of a grump tonite,

Randy,
My research into the Belgians gives a grit size averaging 15 microns, usually 5 to 20 but most around 15. It is their odd shape, roughly a 20 sided crystal that prevents the sharp corners from penetrating the steel more than about 2 microns. This is what gives the very smooth polish they are known for.

Even though they are supposed to be 8000 grit I think Lynn has commented that they cut more like a 12,000 grit stone.

I just got my shipment of new stones today and am working through the waitlist now. I do have a few 2x8 Coticules that are not spoken for and maybe a 3x8 Coticule. Also a few blue stones and a few vintage ones. They are a pretty sight.



Tony

They look to me like a bunch of candy bars to a kid...

Tony, thats interesting. Some time ago I read a description of the belgian hones and they said the avarage size was 6 microns and that the garnets splintered thus giving a finer grit. Oh well, whatever it is it does work well.

How much for the 3X8?

http://www.ardennes-coticule.com/engels.htm

t's due to the garnets. As soon as you start the sharpening, these garnets will leave the stone and, used with water, they create a very "abrasive milk". The garnets have a round or oval form. You can compare it withe a football, that consists of a lot of small leather planes, stitched all together. These planes form obtuse angles. The bottom of these angles are in contact with the steel while sharpening. When the garnet grains are more or less 15 micron, the penetration is only 2 or 3 micron. This is why the stone sharpens so fast and delicately.

Stone of Vielsalm or Coticule
Colour: yellow-white
Fineness: till 8 000 grit
Garnets: 30% till 42%

Belgian Blue Whetstone
Colour: dark blue-grey
Fineness: 4 000 grit
Garnets: 20% till 30%

What's the best stone for my application?

If you need to sharpen very rapidly, till 8 000 grit, the yellow stone is the best one. To sharpen normal knives as carving knives, graver, scissors, the blue stone is sufficient.

Have a look at the source and end the discussion ....

Hoekie

hoekie,
Yep, that would be the source. They alkso mention the yield of yellow to blue stone. Only .66% is yellow Coticule which explains the price.

Tony