Stone types, grits, and what they can do

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bgentry

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Aug 3, 2009
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Hi, I've been doing some research around the web and read a number of older threads here trying to figure out which types of stones cut/grind a certain way and what they are capable of doing.

I have some questions about stones I have, and how their performance compares to some I don't have. Specifically I have:

Norton 8" combination stone: Medium crystolon (Silicon Carbine) / Fine India (Aluminum Oxide).

The medium crystolon seems to cut fairly aggressively, but not overly so. Seems like a good stone for doing rebeveling work and won't kill your blade if you make a mistake. It leaves a rough edge that cuts, but *barely* shaves and definitely needs more polish IMHO. I found this chart which I'm sure most (all?) of you have seen:

Stone Finish and Cut Rate

According to that, coarse diamond cuts roughly 20 to 25% faster than medium crystolon and maybe 10 to 20% faster than coarse crystolon. I can basically believe that from what I've read, but then look at the sharpness. Coarse diamond can get a blade just as sharp as medium ceramic or hard Arkansas, both of which are about 2.5 times sharper than medium crystolon?!?

Is that really true? If so, I can take an incredibly dull blade, and with just one stone, take it up to cleanly shaving sharpness faster than just putting on a rough edge with my medium crystolon? I'm skeptical but I suppose it's possible.

I'm not sure which "medium ceramic" they are referencing, but hard Arkansas should be a fairly fine edge by most standards. I have a Spyderco profile medium (gray) ceramic stick/stone; I'm not sure if it falls into the medium category of that chart, or the fine category. I do know that it produces a very good polish (by my standards) on every blade I've used it on, yielding shaving sharp edges that cleanly cut newspaper from a few inches away from the hold point.

On that subject, I've found the opinion that the Spyderco medium is roughly 12 to 14 microns, or 700 to 800 grit based on it's scratch pattern and perceived edge polish. This posting is where I got that information:

Native Justice's opinion on the matter

Again, I'm not sure if the Spyderco material is a special case for ceramics, or if they are typical of ceramic stone performance. I just know I love the way this stone polishes an edge.

Which leads me to the Spyderco profile fine (white) stick/stone that I have. The guy who sold it to me said, "You don't need it, but I'll sell it to you." He seems to have been more right than wrong. Hand holding it as a "stone", with my skill level, I can barely increase the polish level on most blades I've tried it on, and on a lot of them, I actually make the edge more dull. I don't know what I'm doing wrong, but I know it doesn't work so well in my hands. According the post referenced above, the fine white is 7 - 9 micron or 1000 to 1200 grit; pretty fine, but not insanely so.

Finally, the other side of that Norton stone I listed above: Fine india. I read a posting here by the man who got Norton to build that stone saying that he liked the combo. I don't recall his name but apparently he's written books on sharpening and should know what he is talking about. For the life of me, I can't get the fine india to do *anything* useful. It barely removes any material, yet doesn't polish very finely at all. Which is no surprise since it's only (roughly) 280 grit. I've tried it a half dozen times on a half dozen blades and gotten no where. I generally just ignore it, but I thought I'd ask here.

Oh and for reference for where I'm getting all of these "grit" numbers, I'm using Steve Bottorrff's chart here.

Thanks for reading this long posting. I tried to do research before posting, but I just couldn't find the kind of specific answers I'm looking for. I hope this isn't too repetitive.

Brian.
 
i want to say that i admire your first post,(because i havent had the balls to ask) i will say that i am no pro what so ever at sharpening and would 2nd just about every question asked. Congrats on your first post!
 
Gentry,Realize different people post different grit on products from charts but one is apples the other oranges.They should only be compared within themselves.For instance
a fine diamond stone will state "fine 600 grit but when you compare it to your fine Norton it feel much coarser.So,compare diamond to diamond,India to India stones ect..
By the way the Norton site states the 2 grit stone you mention at 180 coarse and 380 for the fine.I have the same stone and get good results from both sides.Then I take it to a finer stone (that Norton is only a med.fine) like a Washita and on to a Black hard Arkansas and on to strop.You should not just get a knife sharp on a coarse stone then use it.When it could be maximize to a much higher degree. The ceramic stone you mention is a good stone.It delievers a finer edge and takes time getting use to. As do all the finer stones but will greatly help you maximize your knife steel if you decide its worth the effort.They are low metal removal and slower,unlike the coarse stones.
Good luck.DM
 
For most all sharpening needs I have found diamond hones and compounds to be the best. They cut the fastest, last the longest and produce the sharpest edge of any stone I have ever used. Thats not to say they are the best for everything though. For some reason I can only hold a stright bevel on a scandi blade with a waterstone, don't know why this is but they work great for that type of blade. I like waterstones for their traditional feel and they also work very well with high hardness steels but IMO lack the finished sharpness for the given grit.

Spyderco ceramics are also very good sharpening tools but with ceramics you tend to form a larger burr and they don't cut real fast. On the plus side they go to a very fine level and produce a nice even polish with a exceptional level of sharpness. The only problem I have had with ceramics is that with some high hardness steels they tend to microchip the edge, rare but it has happened.

Its hard to explain about the different types of stones, its just something you must do to truly understand. There is a feel and a method for all of them and you must learn the way each works. Stone selection will also depend a lot on the type of steels you plan to sharpen.

For lots of info on sharpening and stones read the following, its older but still very good.
http://mse.iastate.edu/fileadmin/www.mse.iastate.edu/static/files/verhoeven/KnifeShExps.pdf
 
@revhard: Thanks for the kind words. That was a nice welcome to the forums.

@DM: My point was trying to compare different types of stones, so I could figure out their relative performance. I understand your point about the word ratings (coarse, fine) meaning different grit levels on each type of stone. It's kinda crazy that medium can mean 4 different things on 4 types of stones, but I knew that before asking. I'm interested in whether or not the chart, which shows their relative cutting speed and their abrasiveness, is accurate.

As for the absolute grit rating of my Norton combo stone, I've read their literature. They seem to disagree with Steve's chart.

He says medium crystolon is 150 grit or 93 micron, while Norton says it's 180 grit, 78 micron. For fine india, Steve says 280 grit, 43 micron, while Norton says 340 grit, 35 micron. Either way, it doesn't change the fact that I've had no luck in sharpening with the fine india. Again, maybe it's my technique.

Brian.
 
@knifenut: Thanks for the opinions and that link to that paper. I've only read about 2/3s of it, but it's very interesting. I think his methodology is a little bit flawed, but I'd bet that's been discussed to death here already. He definitely did a lot of good tests with pictures at a magnification I've never seen before. Neat. :)

Brian.
 
bgentry said:
@knifenut: Thanks for the opinions and that link to that paper. I've only read about 2/3s of it, but it's very interesting. I think his methodology is a little bit flawed, but I'd bet that's been discussed to death here already. He definitely did a lot of good tests with pictures at a magnification I've never seen before. Neat. :)

Brian.
Click to expand...


Yes, some of the things he talks about I would not agree with today but a lot of it is very technical and helps to understand the more complex side of sharpening. The level of magnification is awsome, wish I had a SEM :(
 
From my own sharpening experience, grit only tells part of the story. The other major factor is the shape of that grit. Are the individual grit particles angular and sharp? Are they rounded and smoother? My DMT diamond hones seem to have sharp, angular grit that produces a crisp edge with bite. The same with my waterstones. With waterstones, I believe fresh grit is continuously being revealed in the water/grit slurry and that's why the waterstones cut so quickly and leave a smoother, better-formed edge.

I've tried norton and other traditional stones. For the same size grit, they seem to leave a less refined edge than the diamond or waterstones. I seem to need to go higher in grit number to get the same quality of edge.

With ceramic "stones" like the Sharpmaker, they seem to remove metal much more slowly and leave a smoother, finer edge than their "grit equivalent" would suggest. I believe this is because the individual grits are more rounded than DMT or waterstones, and I go to a larger grit to get the same degree of metal removal on the coarse side of things.

For the most part, I rebevel all my edges with my DMT stones or the waterstones on my Edge Pro, then maintain a secondary bevel with my Sharpmaker. This saves me time, and takes advantage of of the good qualities of each media.

I got a set of 5 Shapton glass stones that I use on my straight razor. When I get the chance I'm going to start using them on my knives to see what type and with what speed I get results.

My two cents.
 
RobbW: I'm going to summarize what I read from your posting to make sure I got it right:

Diamond: Sharp grit. Leaves a "crisp" edge. Not sure if this means polished or "toothy".

Waterstones: Essentially same as diamond observations.

Norton stones: Don't cut as finely as you'd expect based on grit number. I.E. a 400 grit stone cuts more like a 300 grit stone. I'm assuming you are comparing this to diamond.

Spyderco ceramic: "Rounded" grit structure. Cuts slowly, but leaves a more refined edge than you'd expect. I.E. a 600 grit Spyderco ceramic cuts more like an 800 grit stone.

This stuff is certainly no where near cut and dry. Thanks for the observations so far.

Brian.
 
RobbW said:
From my own sharpening experience, grit only tells part of the story. The other major factor is the shape of that grit. Are the individual grit particles angular and sharp? Are they rounded and smoother? My DMT diamond hones seem to have sharp, angular grit that produces a crisp edge with bite. The same with my waterstones. With waterstones, I believe fresh grit is continuously being revealed in the water/grit slurry and that's why the waterstones cut so quickly and leave a smoother, better-formed edge.

I've tried norton and other traditional stones. For the same size grit, they seem to leave a less refined edge than the diamond or waterstones. I seem to need to go higher in grit number to get the same quality of edge.

With ceramic "stones" like the Sharpmaker, they seem to remove metal much more slowly and leave a smoother, finer edge than their "grit equivalent" would suggest. I believe this is because the individual grits are more rounded than DMT or waterstones, and I go to a larger grit to get the same degree of metal removal on the coarse side of things.

For the most part, I rebevel all my edges with my DMT stones or the waterstones on my Edge Pro, then maintain a secondary bevel with my Sharpmaker. This saves me time, and takes advantage of of the good qualities of each media.

I got a set of 5 Shapton glass stones that I use on my straight razor. When I get the chance I'm going to start using them on my knives to see what type and with what speed I get results.

My two cents.
Click to expand...

Shapton Glasstones cut very fast and leave a great polish and high sharpness for their grit rating. I have the 1000, 2000, and 8000 grit Glasstones and just love them. I use DMT Diasharps for XX Coarse, Coarse, and Fine grits, and they work extremely well for me. They also flatten waterstones very nicely. I use Spyderco ceramics sometimes instead of the Glasstones, and they leave a great finish, but as you do I only use them for microbevels. For me the huge speed advantage and greater polish of the 8000 grit Glasstone compared to the smaller UF Spyderco benchstone makes the waterstones my favorite for full bevel sharpening. I I know Knifenut has great results with the DMT XX Fine, but I don't want to do the extremely long break in process to get those real pretty edges with that stone when my Shapton Glasstone in 8000 grit (1.84 micron) leaves a mirrored, very sharp edge for me already. If I only had my old Norton 8000 grit waterstone I would have bought that DMT long ago for my 8000 grit needs, as my Norton loved to gouge and dished quickly. The Shapton Glasstones are so resistant to dishing and gouging while leaving a great finish while cutting fast that I have just stuck with them while using DMT's great coarser grit stones for rebevelling, sharpening & flattening. So far, so good with them. The Sharpmaker or Spyderco benchstones are great when you want quick, no mess results on a microbevel, but the Shaptons have made me a waterstone man.

Mike
 
Besides grit shape and hardness a hone is influenced by the hardness of the substrate. A strop or waterstone has a relatively soft substrate. You need to be honing/stropping at close to your original bevel angle or you risk rounding your edge. There is a bit more art to putting on a final edge using a waterstone than you might expect.

A ceramic hone is not an aggregation of semi-distinct particles (grit). It is more fused together into larger blobs of glassy material. The glassy blobs wear flat on the top. In a sense it works more like an ultra-microscopic grooved file than sandpaper. The hardness of the matrix is great for micro-beveling since your edge won't dig into the hone when stroked edge-first.
 
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