Thread: A theoretical discussion about honing particles

Originally Posted by majurey

So that would make them variables?

I guess so Nah, they are constants whose specific value depends on stuff. One might call them parameters, in fact. Damn editors ....

James.

Originally Posted by Wildtim

Bart, you are a little confused.

What you are calling grit count is actually known as mesh size.

The mesh is a sifter used to size the cutting particles found in hones and on sandpaper. The number references the number of holes per square inch in the mesh. In the industry I'm sure there is a standard size wire used to weave the mesh out of as well. once you have your sifted medium you then incorporate it with a matrix material giving you the components of a man made hone. While particle shape does effect the aggressiveness of a hone, its speed is also very much a factor of the proportion of cutting medium to matrix in the particular hone you are using. Thats why a Norton is faster than a Sun Tiger hone, they probably use exactly the same medium just in far different proportions.

I am confused about the mesh that the particles are sifted through. If you, for example, were to us a mesh that has 300 holes squared per inch then when you sifted the particles you would get everything smaller than the 300 holes per inch mesh. It would seem to me that one would have to resift using say 305 holes per inch to sift out the smaller particles. From a quality control standpoint one could then say that I have a bag of particles that had a size that was between 300 and 305. No?


Thanks,
Richard

I posted a conversion table of American grit, Mesh and Particle size earlier in this thread. The mesh numbers are the range of particle sizes in microns since meshes at these small sizes don't exist. Mesh is a theoretical calculated number not a screen since as I said, meshes of this size don't exist. So, an 8000 grit has a mesh or range of particle sizes form 2 to 4 microns and an average particle size of 3 microns. Above 400 grit, particles are not seperated by actual meshes but by other processes which are mostly of interest to mechanical engineers involved in grinding technology.

Thanks for starting this thread, Bart.

There are a lot of good points brought up already, I'm just going to add some more variables and stir the pot and see what floats up!

Particle density... take abrasive papers, there's open coats and closed coats. Each could be sold as 400 grit but is it possible to have the same grit size on both papers? The same can be done in hones, more binder=less grit, less binder=more grit. Low volume of dense binder ~ closed coat. High volume of porous binder ~ open coat.

Cutting pressure, often forgotten in our discussions. Take two hones, one with spaced out open coat grit, the other dense closed coat but both have the same grit. One will cut faster than the other, one might create deeper scratches than the other. Why? Cutting pressure. The bevel rides on the tops of the grit particles on the surface of the hone. More particles means less pressure between each particle and the bevel but more scratches in the bevel for a given distance of movement. Coarse open coat means more pressure between each grit point and the bevel means fewer, but deeper scratches for a given distance of movement. This will change during honing... swarf will build up in the areas between the grit... big space, lots of room, little space, little room. If open coat, grit will dull faster as there are fewer in contact with the blade but won't clog up... closed coat won't dull as fast but might clog up with swarf reducing contact with the blade... Lubricant has a large effect as well, water, lather, saliva or what have you.

The grit itself, let's say aluminum oxide... it could be mined or it could be man made. If mined, how pure is it? If man made, was anything else added to the recipe to modify it's performance. How was it crushed to make the grit? There are various types of mills... one might produce duller grit than the other. How carefully was the screening done, how much time does a manufacturer spend on this kind of work? All these things add up and there is no way for the end user to predict the outcome except by trail and error for his/her particular situation. There is an almost unlimited number of variables that can affect the outcome.... I just don't see how we could distill this down to something basic. We can however come to realize that the more we know, the more we know we don't know!

So in the end, we'll be back to doing what we've always done.... Hey, anyone ever use this type of hone? You did? And it works OK for you? Great... I guess I get one and give it whirl then, maybe it'll work for me.....

Regards

Christian

Hi guys, I deleted an insulting post, and asked the poster to simply not participate if he thinks a topic is boring, and not to belittle those who enjoy it.

I deleted the post because I don't want people (esp newbies) to feel discouraged from discussing every last minute detail of honing (or whatever else). If you wouldn't feel comfortable discussing those things here, then where else would you?

I also deleted a couple of follow up posts that responded to that original post. Not because I don't agree, but because they don't make sense without the original post, and also because I don't want this thread to contain a large offtopic tangent that detracts from the original discussion, and might even unravel it completely.

As you were. Have fun

Originally Posted by blaireau

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 blaireau

I posted a conversion table of American grit, Mesh and Particle size earlier in this thread. The mesh numbers are the range of particle sizes in microns since meshes at these small sizes don't exist. Mesh is a theoretical calculated number not a screen since as I said, meshes of this size don't exist. So, an 8000 grit has a mesh or range of particle sizes form 2 to 4 microns and an average particle size of 3 microns. Above 400 grit, particles are not seperated by actual meshes but by other processes which are mostly of interest to mechanical engineers involved in grinding technology.

So in my browsing for stones I've noticed that all the ones I've looked at list the specs for a stone in both grit and microns. Actually I got the impression that maybe the grit was more of a "name" for a loose comparison. For example:

Shapton (glass) 8000: 1.84u
Norton (water) 8000: 3u

This is a significant difference in particle size right?

I guess there is a followup question. The table you provided had a label at the top "American Standard (Grit)".
How "standard" is the American Standard? Is it one of those standards you can go to an independent certification company to get your product certified?
And then, are all/most hone companies using that standard? Internationally?

Originally Posted by Bruno

Hi guys, I deleted an insulting post, and asked the poster to simply not participate if he thinks a topic is boring, and not to belittle those who enjoy it.

I deleted the post because I don't want people (esp newbies) to feel discouraged from discussing every last minute detail of honing (or whatever else). If you wouldn't feel comfortable discussing those things here, then where else would you?


As you were. Have fun

Hey Guys, It was my post which was deleted, I would like to apologize for putting a negative spin, however unintentional, still not my place. My intent being irrelevant at this point, still I would like to extend my apologies, and grattitude to yall for being so helpfull regardless of one being a dumbass. Again I was wrong in the manner in which I posted, and for that I apologize.

Thanks,
Paul

You really can't compare a natural stone to a synthetic one. natural stones can have the cutting medium, say garnets of all different sizes and particle shapes. Hopefully what makes it a superior honing medium is that the particles are as uniform as your ever going to get them in a natural stone.Synthetic stones use manufactured particles so hopefully they are better sorted for uniformity. I know when you buy diamond compound what diferentiates the more expensive stuff from the cheaper stuff is the degree of sorting that goes on so the uniformity is higher in the better compound. Years ago I used to go mineral collecting at a garnet quarry in Connecticut and the rock had garnet xtls ranging from 1/16th of an inch up to a inch across and pieces of garnets in micron sizes. I don't think that rock would make a good honing stone.

In the DMT system of grading, a Coarse stone is 45 microns and 325 "mesh equivalent". The Fine is 25 microns and 600 mesh equivalent. The Extra Extra Fine is 3 microns and 8000 mesh equivalent. Their ceramic stone is 7 microns and 2200 mesh equivalent. Their Gray Diamond compound is 1 micron and 15000 mesh equivalent.

I think some of the confusion in all of this is that there is a standard for artificial stones be they diamond or ceramic but for natural stones? Not so much. I've long maintained that I feel the Chinese stones, for instance, are misgraded. As some astute person mentioned in a previous post, it probably has a lot to do with marketing the hones and we all know how marketing goes!

Quick, the American Standard Grit is one of several standard grit systems. even the two examples that you cite:

Shapton (glass) 8000: 1.84u
Norton (water) 8000: 3u

fit within the AMG in that the mesh which is a measure of the range is 2 to 4 microns for 8000 grit and so the Norton for sure is in this range and the Shapton at 1.84 microns is close enough to 2 microns to qualify for an 8000 grit rating. I think that your comment about "loose comparison" is more properly stated that the mesh is a range, we can't guarantee that every particle is 3 microns for an 8000 grit stone but rather that the average size tends to be that size. So when comments on natural stones classify them by grit number, the comments more refer to that the natural stone cuts or polishes like a given grit size man-made stone. The bigspendur is right that natural stones can't tightly conform to to the grit standard like their man-made counterparts. To pin this down exactly, a good size piece of your natural stone would have to be sacrificed to ascertain the actual grit and then we would have to ponder how the pulverizing process affects the abrasive particle size. A man-made stone doesn't have this issue since we purposely take the proper cut mesh of the abrasive to create the stone at a given grit.