ceramic or water stone

[Jason B.]

I have one 800 grit water stone that works great for re-cutting a edge but all of my other stones are spyderco ceramic. even at 800 grit it seems to leave a nice dull polish I guess my question is, will the water stones at higher grit levels create a nicer [shinier] edge with less micro scraches than the ceramic. this is not a question of sharpness just of edge apperance .

 

[matt321]

Well, I would assume the grit rating would give a fair indication of what to expect. Spyderco Ceramics are 20, 9, and 7 microns (medium, fine, and ultrafine). Waterstones can be had from 120 microns down to 0.5 microns.

Maybe you mean when compared at the same grit. So would a 7 micron ultrafine ceramic leave a more polished edge than a 7 micron waterstone?

 

[Larrin]

You could get the best of both with the ceramic Shapton waterstones. They don't need to be soaked and they use the hard ceramic abrasive, but they use a substrate so the stone wears for faster cutting action, unlike the pure ceramic Spyderco stones which cut slowly.

 

[Jason B.]

thanks for the micron ratings on the spyderco stones nice to know. what i mean is when you look at the scratch pattern on the edge, after using the med. grit ceramic the scratch pattern looks larger than with the 800 grit water stone and the water stone leaves a more hazed look than a scratch.

 

[yuzuha]

Ceramic has smoother rounded abrasive so tends to pull up hunks of metal that will ball up and gouge the surface as well as leave nice smooth shiny areas where it has smeared the metal while waterstones tend to have sharp abrasives that leave a more even but more matte looking surface.

Here is a micrograph of a block of stainless I polished with a 5k waterstone
5k waterstone
then I polished it on a spyderco ultra fine... lots of smooth shiny areas but tore gouges in the surface.
spyderco UF
then I repolished it a little with a 10k waterstone
repolished at 10k

The last image clearly shows the gouges left by the ceramic and the small diagonal scratches from the 10k.

 

[Jason B.]

now you have got me thinking should I switch to water stoned?

 

[Jeff Clark]

That's a nice collection of micrographs, but it represents a flat block of stainless rather than a knife edge. Working on a flat surface, such as the large bevel of a woodworker's plane, the soft matrix of the waterstone helps to evenly distribute pressure and grit. You get a nice flat finish. The soft matrix also allows grit to move out of the way when pressure builds up to help prevent gouging or galling.

The big issue is that things are different when you tilt a blade to hone an edge. In that case the edge can gouge into the soft waterstone matrix and let it gouge, chip, or round the apex of the edge. It takes a light touch to optimally microbevel an edge using a waterstone. When you microbevel with a ceramic hone the edge does not dig into the hard ceramic surface. The ceramic abrasive tends to be more flattened on the top to leave a smoother finish. You need to clean the ceramic or debris will tend to stick to the surface and cause galling. This is less of an issue when you are microbeveling since there isn't much area for debris to collect between the hone and the blade (the contact area is very small). The edge also tends to displace debris from the hone. I don't think that you would see anywhere near as much galling of the edge during normal honing.

I had a question about the micrographs. What type of stainless was used for the sample? It kind of looks like it was a soft alloy from the amount of galling. Was it a full 56RC hardness knife alloy?

 

[sodak]

I've had much better luck with my ceramics than with my waterstones, don't really know why. I mainly use my waterstones for my straight razors, ceramics for everything else.

 

[matt321]

Pro's: The Spyderco bench stones don't need routine flattening and they don't require water or oil during use. They cost about the same or a little less than good waterstones. (The sharpmaker version would be the cheapest way to go.)

Con's: They are slower cutting than waterstones. They load quickly and have to be scrubbed clean.

I like the micrographs. Hard to imagine the ultafine could leave that pattern. It feels like a slab of glass. I think it rates 2,000 grit on the waterstone scale.

 

[yuzuha]

Hi Jeff. The steel is a block of whatever they use to make the head mounts of mainframe disk drives, and appears to be similar to the steel my Lamson Sharp paring knife, so yes, it is softer than the Rc 60-68 stuff in my Japanese knives. The surface was a 3/8" side of a 1.5" x 1/2" x 3/8 block, polished under running water to help keep the stone from loading up, and magnified somewhere around 2400 times including digital magnification. All 3 surfaces looked like a mirror to the eye with some barely detectable streaks on the Spyderco surface (the scratches and gouges were invisible without magnification).

Waterstones vary in hardness. You could easily gouge my Naniwa 10k, which I mostly use on hard steels (cuts faster and less apt to damage an edge due to freehand slop), while my Shapton pro 15k is so hard that it won't gouge if I try (use that on softer steels as the hardness helps better control the edge shape). My awase is on the hard side of medium and does a good job on carbon steel knives.

Matt, here is the spyderco ultrafine stone surface of spyderco UF The grit is pretty large (appears to average around 7-15 microns), but is rounded and in a very dense, hard matrix so it cuts more like scraping with a bit of clam shell (doesn't really penetrate into the steel so much as scrape off the high spots) rather than scratching like a sharp pointy crystal (which does penetrate into the steel and plows a furrow) . The grain shape and dense matrix result in a much smoother surface than you would get from an India stone or waterstone with the same size grit (except for the streaking, it looks similar to about a 5k to 8k waterstone finish)