Thread: A theoretical discussion about honing particles

Originally Posted by ArdennesCoticule

Grit is the number of 'particles' in one square inch surface. So in case of our Coticule and BBW stones this is the number of garnets in one square inch surface.
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According to what standard though? Per the European FEPA system? As I cited in my above post, there are several different systems for determining "grit" and they deviate wildly when you get into the finer abrasives.

Also, how did you determine the size of, and number of, particles per square inch? Destructive testing of coticule and belgian blue samples?

I'm not being combative, just curious. I really like my coticule and belgian, and want to know more.

I am with Bart on this subject. I also feel that the particles per square inch, size of the particles, what the particles are made of [garnets, diamond, ceramic etc] and what shape the particles are, effect how they cut and how smooth the edge becomes. My observation of the DMT 8EE 8K seems to make my edge a lot rougher than a Norton 8K or Shapton 8K which makes me believe that there are less particles per square inch. This would allow the diamonds to cut deeper into the steel per stroke. I don't have any scientific evidence or proof. It is just an observation and feeling.

bj

There are standard ways to relate Grit, Mesh and Particle Size. Please see the table below, it's just that simple. Bart, please don't burn up your slide rule on this one, it has all been worked out! Enjoy gents.

Originally Posted by joke1176

According to what standard though? Per the European FEPA system? As I cited in my above post, there are several different systems for determining "grit" and they deviate wildly when you get into the finer abrasives.

I have to admit that I have no idea! I'm just repeating what I learned of my father. My father learned this from his predecessor and so on.

Originally Posted by joke1176

Also, how did you determine the size of, and number of, particles per square inch? Destructive testing of coticule and belgian blue samples?

The size, shape and number of particles are different for each stone. It's a natural formed stone.
We had a lab testing our stones about 10-15 years ago.

Well technically (we are in the advanced honing section) I'd imagine that mesh or grit or whatever is some measure of central tendency per square inch (or whatever). An average, for example, or a median. Or perhaps a maximum number per square unit. It is highly unlikely, however excellent the manufacturing or natural process that generates the hones is, that there is uniformity across the entire stone in this regard. There is also variability with regards particulate size - again, I would imagine that a measure of central tendency such as a mean or median size is what is being quoted in this regard. Or, given things are run through sieves, perhaps a maximum size is quoted. In any event, both the size of the individual particles, and how many of them fit into a square unit of hone, is variable. How much variability there is will effect the working of the hone in my mind.

When it comes to converting grits to microns it appears it is not exactly as simple as "one chart fits all". Based on a little analysis I did a while back, the constants in the conversion formula vary depending on who (manufacturer, and their processes/medium/particle geometry etc...) you are talking about. The relationship is basically an inverse one (of course). For those interested the results are here.

James.

Grit is a measure of the particles that go through a certain size mesh and as such can be related to a particle size. The relationship can be derived from the chart I published in my first post to this thread above. It is a logarithmic power law equation and when expressed as such it has a better than 99% fit. It isn't simple but it can be understood. As you can see, though many have asserted that a Belgian Blue has a 4000 grit and a Coticule an 8000 grit, the actual grit that relates to these stones is more like 1200 to 1800.

Originally Posted by blaireau

Grit is a measure of the particles that go through a certain size mesh and as such can be related to a particle size. The relationship can be derived from the chart I published in my first post to this thread above. It is a logarithmic power law equation and when expressed as such it has a better than 99% fit. It isn't simple but it can be understood. As you can see, though many have asserted that a Belgian Blue has a 4000 grit and a Coticule an 8000 grit, the actual grit that relates to these stones is more like 1200 to 1800.

Well yes, I've been saying that for quite some time now, glad someone confirms it.
Of course, I completely understand why they can't be sold as such, and they really shouldn't, but for understanding how they work it's good to realize they don't have the particle size of the fine synthetic hones, such as produced by Naniwa, Norton, Shapton, DMT and others.
The Belgian hones don't derive their brilliance from a high grit rate, and that's what makes them so unique. Apart from my disorienting mumblings about the math of grits and particle sizes, I consider the real highlight of my first post to be in the drawing. It shows that , in theory, and without considering plastic deformation, a large round garnet-like particle can create a keener edge than a considerably smaller spike-like particle. It also shows how a fast (hence deep cutting) spike-like particle renders an edge into a wire edge when the scratches of both sides start meeting each other at the very edge.

I haven't made a drawing of two sizes of round garnet-like particles, but I would like to formulate a daring hypothesis:

The Belgian Blue Whetstone has larger garnets than the Coticule.
IF those larger garnets have more facets, than those facets will be obtuser than the Coticule's.
For that they will cut smoother curves.
For that they will exert less PSI on the steel, leaving a shallower scratch pattern.
The Blue's slowness in relation to a Coticule seems to confirm this.
IF all that's true, and IF the principles that my drawing shows are sound;
then the Blue will allow a keener edge than the Coticule.

I have already testified on another thread about the Blue with slurry leaving a keener edge than the Coticule with slurry. So have Josh Earl and David Polan (Heavydutysg135) testified before me. What about the Blue with water, then? I've always considered it too slow to give it a serious try. But aren't some top dollar Japanese Natural hones not considered too slow as well for use too early in a progression? What if I dismissed the Blue with water, simply because I failed to realize I was using it before its time?

IF SO, an ideal progression might be:
1. Coticule with slurry till bevel is set and keennes levels off.
2. Belgian Blue with slurry to refine the edge till keennes level off.
3. Coticule with water for 100 laps.
4. Blue with water for 100 laps.

High time I got away from the laptop and started honing...
I'll keep you guys posted.

Bart.

Originally Posted by Bart

...IF SO, an ideal progression might be:
1. Coticule with slurry till bevel is set and keennes levels off.
2. Belgian Blue with slurry to refine the edge till keennes level off.
3. Coticule with water for 100 laps.
4. Blue with water for 100 laps...

I have been pondering what you are pondering... I am going to be tied up all weekend and most of next week, but I may try this myself.

Plus which, The iron oxide matrix that binds the garnets in the coticule is slightly abrasive also. I found an article a while ago when I had access to the University's full text databases.

For the life of me, I can't find a goddamn abstract anymore, so I can't back up my claim...BUT I really read it somewhere. Honestly.

Originally Posted by joke1176

I have been pondering what you are pondering... I am going to be tied up all weekend and most of next week, but I may try this myself.

Plus which, The iron oxide matrix that binds the garnets in the coticule is slightly abrasive also. I found an article a while ago when I had access to the University's full text databases.

For the life of me, I can't find a goddamn abstract anymore, so I can't back up my claim...BUT I really read it somewhere. Honestly.

Fascinating discussion! I'd love to see where this goes.

FWIW I thought that Howard or perhaps someone else confirmed that the garnets in the blue Belgians are no bigger nor smaller than the yellow - they're just less numerous, hence the slow cut. Perhaps the gentleman from Ardennes can shed some light on this.

Regards,
EL

Originally Posted by Jimbo

the constants in the conversion formula vary ...
James.

So that would make them variables?