The reoccurring question of grit

I have not been here long, but it seems that there are a ton of questions on grit size. For instance, "what grit is a coticule/escher"? comes up a lot. From what I can tell, central to the problem is the different grit standards used.

Why hasn't anyone compiled a list of available honing surfaces and equated them with some standard such as microns? It would be nice to see all of these hones and pastes together on a single scale from coarse to fine.

Now I realise that particle size is not the only factor, and there are things that set each surface apart from one another such as the speed of cutting, etc. Still, what could be the harm in such a list as long as the viewer realized that the list was not created to imply that one surface was "better" than another?

Is there such as list, and if not, why not create one? I'm a graphic artist, and I'd love to make one if someone would help with finding the data.

I think there is also the problem of how variable the grit is and how you measure it.
Say you had a stone that said 8K.
Is it an average grit of 8K with some parts being more or less than 8K or is it a minumum particle size of 8K?
Is this right? Is it to do with how each company measures their stones?
I'm sure some of the more experienced members can explain more clearly why there is no specific answer to grit size.

Nick

There are lists for synthetic stones but once you include natural stones the ability to list them kind of falls down as stones of the same makeup perform differently.

It's even more complicated than that. Some stones with known particle sizes perform very differently from what you'd expect. The coticule is a good example of this - from what I've read the grains in the coticule are roughly 15 microns across, yet it performs comparably to diamond hones with 1 micron grains because it makes such shallow scratches.

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Originally Posted by mparker762

- from what I've read the grains in the coticule are roughly 15 microns across, yet it performs comparably to diamond hones with 1 micron grains because it makes such shallow scratches.

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Holy Cow, that does complicate things. Thanks for the link. That information really sheds some light on the subject.

Perhaps on a grit chart the natural stones should be placed according to their effective grit size, with a note as to why of course. In this case I'm guessing the coticle should be placed around 1 micron.

Quote:

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Originally Posted by mparker762

It's even more complicated than that. Some stones with known particle sizes perform very differently from what you'd expect. The coticule is a good example of this - from what I've read the grains in the coticule are roughly 15 microns across, yet it performs comparably to diamond hones with 1 micron grains because it makes such shallow scratches.

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I think that's the key to this whole thing. Every material behaves differently so there is no universal key. What you would need is a series of bar graphs with each material and then line up each bar to correlate with the different materials.

Actually someone around here did that because I know I saw it. Possibly a link from a post but I remember it was a series of bars with the synthetic ceramic in the middle and the other materials relating to it. Its gets very compicated the more media you include.

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Originally Posted by thebigspendur

...I remember it was a series of bars with the synthetic ceramic in the middle and the other materials relating to it...

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http://users.ameritech.net/knives/speed.htm

Could this be the one? I found it searching through the forum history...

The concept of grit size has to do with filtering abrasive particles through mesh screen. So, the grit "size" has to do with how many wires per inch make up the mesh. Of course, since not all countries use the inch, there are several standards around the world depending on units of measure. These standards also have differences in the range and amount of grit (of a given size) which may be contained in the result.

So while you can easily compare the mesh sizes between the standards, you have to realize that the mesh size is only part of the criteria you need to consider when comparing the effectiveness of different abrasives. The cutting action of the abrasive will vary because of the population differences of various sizes of grit within the mix, the shape of the abrasive particles themselves, how well the particles hold their jagged edges, the openness and flexibility of the binder which holds the particles together, and numerous other factors. When you consider all these variables, its no surprise that an 8k stone from one manufacturer and a 12k stone from another manufacturer perform similarly.

If you do some searching in the forums and the help files you'll find a number of references and graphs. The question becomes once you can compare grits, then what? ;)

I don't know if anyone is interested in this or not, but here are some charts I have found on the subject of grit sizes. As has been discussed, its not clear what grit size really tells us about the potential to sharpen, but here are the links none the less:

http://www.uama.org/Abrasives101/101Standards.html
http://www.fine-tools.com/G10019.htm
http://www.silversmithing.com/1abrasives.htm

The following links I found through the forum search:
http://www.belgischer-brocken.com/be.../faq/index.php
http://users.ameritech.net/knives/speed.htm

Yea Joe's right even with a chart you have to actually use the stuff to see how it behaves for you so the charts are of little help. You might find that your results are very different than the charts indicate.