On the sharp end of sharp

[not2sharp]

You can sharpen a knife, or any knife, from now to doomsday and it will never be sharper then the medium that you are using to sharpen it. It takes a really fine stone to put a really fine edge on a blade. We have frequenly discussed knife steels, and some steels do have a tendency to develop microserrations that can cut very agressively, while the better quality steels tend to hold their edge longer; but, even the poorest of steels can take on a very fine edge. It all depends on how you sharpen them, and what you sharpen them with.

Lets talk about some of the stones on the market. As I write this I have in front of me a wide assortment of sharpening devices that I have accumulated over the years. There is a Norton stone, a Gatco shapening set, Several DMT products and some Spyderco sets, a buck EZ-lap, and even a Block sharpening steel. Clearly, one maker's definition of fine can be another's corse, and some knives seem to perform their role better when their edges are finished with rougher stones.

Ideally, I would like to finish each edge with ever finer grit stones until I find an edge that works for me. The problem is that the grit is rarely indicated in a useful way. Are the Spyderco professional files finer then the Gatco "fine" stones? They certainly appear to be (especially the white stone); but by how much?

Let's discuss.

n2s

 

[WadeF]

I used to try to get the sharpest most polished edge on my blades, but then I realised that type of edge is pretty useless unless I'm trying to shave with it. So I stopped going to ultra fine stones and putting a mirror polished edge on my blades. The only thing it's good for is looks and saying "I can slice a hair!"

If you're using your knife to slice things open, cut through card board, etc, you really only need to finish with a medium or fine stone. I have heard of people sharpening knives with a file if they need a more aggressive toothy edge to rip through boxes, rope, or whatever. So I think it all depends on what you want your edge to do. On a kitchen knife where you want to slice through tomatoes or something you might want to go with a finer finish.

 

[Cliff Stamp]

not2sharp :

The problem is that the grit is rarely indicated in a useful way.

The most sensible would be the abrasive size in microns, this would clear up a lot of the incoherent numbers. However this doesn't deal with the fact that some abrasives like SiC break down and others like Diamond do not. This means that the finish will be very different even if the base particle size is identical.

-Cliff

 

[not2sharp]

I am surprised that we are not as serious about our sharpening stones as we are about our knife steels. Putting and maintaining an edge on our knives is at least as important as edge retention.

Calling a sharpening stone "fine" is about as useful as calling a grade of steel "surgical".

However this doesn't deal with the fact that some abrasives like SiC break down and others like Diamond do not.

That's another issue. Our sharpening systems should be rated for specific RC ranges. Otherwise we may end up polishing our sharpening stone instead of putting an edge on our bladeware.

n2s

 

[Danbo]

I rarely find it necessary to sharpen much beyond a fine/red DMT diamond stone. Even their extra fine/green stone is a little too polishy(hey, did I just make up a new word?)

 

[Cliff Stamp]

not2sharp :

That's another issue. Our sharpening systems should be rated for specific RC ranges.

To clarify, SiC and AO stones don't break down on certain steels, they behave this way on all knives. While the abrasive particles are very hard (SiC > AO), they are very brittle and are easily broken when honing. Thus those types of hones always give much finer polishes than abrasives that don't break down (diamond and ceramic) even at the same grit level (or even more coarse).

Awhile ago I was honing a knife using 80 grit SiC lapping compound and noting the size of the microteeth, as a slurry started to develop I kept honing to see the effect on the size of the microteeth (x20 mag), after a short while the teeth had been reduced to half the size and the paste was a much finer mud instead of a gritty suspension.

Now to get even more complicated, some of the AO hones break down much faster than the others, Japanese waterstones for example lose particles much faster than the Norton oil stones. This is why the Japanese ones cut much faster even at the same grit level as you get a more steady flux of fresh particles where as the Norton ones just round over.

Steve B. also has considerable reference information on stone grits on his webpage which inclues the abrasive size in micron for most of the common stones and comparisons on rate of abrasion and level of finish. It would be nice if this information was more widely known and included with the promotional material for the hones, few do this, Lee Valley does.

http://www.ameritech.net/users/knives/sharpeningmadeeasy.html

-Cliff

 

[yog]

I think it's probably too hard to be subjective about how fine a sharpening system will go without trying out the various systems yourselves.

Example, I used to think the fine (white) stones on a Spyderco Sharpmaker were as fine as glass, then I got the extra fine (also white) rods for the sharpmaker and even though I can barely tell the difference by rubbing my thumb along the rods, the result on the edge makes the fine rods seem like coarse, I can actually hear the difference when sharpening.
Then again, the polishing tapes on my Edge Pro make the SPyderco extra fine stones seem like a chunk of wood dipped in glue and then stirred through a grit bin. These tapes put a literal "mirror" finish on the edge.

WadeF has a very valid point though. The polished edge isn't necessarily the best, in some situations it's the absolute worst.
I have a knife that I keep for rope and cardboard. I sharpen it to a 200 grit waterstone so that it will "bite" well, but at the same time it is full flat ground with an approximate 26 degree inclusive edge bevel. A bit much for chopping, but it sails through rope and garden hoses.

 

[slices]

Not2sharp, good points. That's why I started the thread "strops & techniques". For as much money, time & effort we devote to our hobby, it seems that there is very little real help for people to standardize their sharpening efforts, or just to learn how. It's more trial & error at this point, which could be a big mistake on an expensive knife.
Yog highlights the differences between the EdgePro & the Sharpmaker very well, & I personally feel that with those 2 tools you can create & maintain Any edge you like with a bit of practice.
But a sharpening forum would definatly help people learn quicker & might just help standardize things if we start adding stuff like Cliff's post. Very good for understanding what's going on at the edge , using different mediums. This gives a better handle on what kind of results to expect, before you start.
Personally, the EdgePro is the tool of choice for me. The main benifits are that the waterstones are very fast cutters and the design of the tool lets you maintain a very consistant, repeatable, angle. I'll try to get the grits for the Sharpmaker stones & post em. I DO know that the green chromium oxide stick that you can get from Rockler's is .5 micron and this translates to about 9000 grit.

If we can't start a sharpening forum, then maybe we can at least standardize the Post subject with the word "sharpening" for easy search retrieval.
There's a huge amount of info in these forums already, but it's pretty hard to get to sometimes. BTW, Radio Shack has a great little 30X lighted magnifier if you really want to get small

 

[Practical Use]

I really enjoy sharpening knives. I have found in the last year there is one really great test for sharpness - does it cut the stuff I want it to cut will very little effort?

I found that the yes answer comes most often without highly polished edges. I really don't care if a knife will shave hair. I do care that it cuts up cardboard boxes like they were butter.

I find myself "over polishing" and then going back an roughing up the edge a little.

 

[panella]

I always enjoy reading commentary and opinions on sharpening on the forums. Just about always learn something. I always hear a lot about the Sharpmaker. I'm an EdgePro user myself.
But I'm starting to look into leather hones with various silicon carbide powders/grits. I've seen almost nothing lately mentioning this method on the sharpening threads. (I haven;t done a thorough search).

Anyone out there use multiple leather hones to sharpen? I'd like to know how these compare to other methods and media. Whether they are effective and what they are most effective for?

 

[Cliff Stamp]

panella :

... leather hones with various silicon carbide powders/grits

This is the same as sandpaper on soft backing, a search on "mousepad" will turn up many links. You can also use the powder / paste on hard backing, wood for example, this then is no difference from a regular benchstone. The only real advantage is the ease (low cost) of getting a large number of grits. A set of sandpapers covering 80 to 8000 grit can be had for a few dollars, covering the same full range with japanese waterstones is around $500.

-Cliff

 

[panella]

Cliff -

No kidding? I guess that makes sense if you think about it. So sandpaper is sort of like an inexpensive, semi-disposable stone. I'll check out the links.

Much thanks for the clarification.

panella

 

[Cliff Stamp]

Yes, the only problem is with long term or just repeated sharpening the cost of sandpaper goes up relative to a hone. It takes a lot of sharpenings to wear out even a small hone. I have a set of 1x4" waterstone I use for most sharpening, and I do a lot more cutting than necessary with many knives on very abrasive materials (carpet and such), and after years of use the 1000 hone still has many years left and the 4000 hone doesn't look used. The more coarse hones break down faster, but trying to wear out a 200 grit waterstone will take a lifetime for most people.

-Cliff