DMT Diamond and Spyderco Ceramic stones

[Larus8]

First thread on here, I hope it is helpful and starts a good discussion.

I am not a knife maker, well, at least not yet. I have a bad habit of starting new habits. I have been reading here about steel and sharpening as I am a traditional woodworker and spend a lot of time on chisels, planes, hand saws, and some power tools like my jointer that have blades that need sharpening. I have tried carborundum, various arkansas, water stones, diamond stones, ceramic stones, and probably something I have forgotten along the way. Currently, I am using several DMT diamond plates (Diasharp) and the medium, fine, and super fine Spyderco bench stones.

I have also tried the scary sharp system which does not work for me. My biggest task is flattening the back of blades. I do the entire back and work until I have a good polish. I have many reasons. One that should interest all blade owners is that a polished blade, with no oil, wax, or other coating, repels water. And, that rust gets started by water or sweat sticking to a blade by adhering to the tiny scratch marks left from honing where polishing was not completed. Try this with one of your small blades and splash water on it. Clean it off with alcohol and splash water on it again. If you have never run this test, you will probably think there is oil or wax on the blade. The water beads up and runs off.

Scary sharp probably works ok for knives or very small blades. On large plane blades, the inconsistent surface of the sand paper shows up in the final results. You can go back and forth indefinitely and get slightly different results each time. For me, the only thing that works really well is a flat, stable, stone surface.

First, carborundum. I have several. These are the very affordable grey stones with a course and medium side. They can be used with water or oil. Carborundum is very hard. It will sharpen almost anything. It is a little soft for carbide. But, it is good on just about anything else. I have a dozen or so carborundum stones. I use them on axes, lawn mower blades, restoration of very old steel, and for flattening other stones. Carborundum stones wear away as you sharpen. This means you get new abrasives as you go, and you have to be careful to not loose flatness too much between lappings.

I have numerous arkansas stones. I like them. They work well with water and oil. (BTW, try baby oil for your sharpening oil. It is cheap, thin, and high quality.) They are a little slow and the range of sharpening action is limited. There, I just made up a term. I like sharpening action because grit density, grit size, etc., are very misleading. That is a very long discussion and I will not bore you with that now. If you are used to synthetic stones, you will probably not like the inconsistency. All of the hard, steel cutting abrasives in the stone are not exactly the same size. The surgical black and the white get very close to consistent grit. But, it is a natural stone. Arkansas stones also wear away as you sharpen.

I have many water stones. I do not use them. That is a long discussion and you probably know more about them that I. My problem is the wearing that generates sharpening speed, and quickly turn disastrous while trying to flatten the back of a blade. It can be done, but it is just not for me.

 

[Larus8]

Within the last year I have learned that my diamond stones were not the end all be all. I have no idea what brand they were. The diamonds are in place and are not clogged, but no longer bite into the steel. I have been replacing them with DMT. And, this brings me to the point of this thread. I have read several things about these stones and have worked out my own solution. First, my X Course has inconsistent abrasive placement. It is mildly annoying, but I can live with that. My fine and XX Fine have good consistency and density. As reported on here by others, these stones are not always flat. I looked at the bottom of each one and discovered they were flat. But, the diamond side was not. Hmmm. That must have something to do with the process of depositing the diamonds and the nickle. Anyhow, I found most of them are flat across the narrow dimension, but have a dip in the middle across the long dimension. I tried something that worked. I put a shim on the bench, clamped the stone to the shim, and then clamped each end down to the bench such that the plate was bent slightly in the opposite direction of the dip. It took a few tries but eventually I got each stone flat. Be aware that I am talking about a few thousands of an inch. Please do not torque your stone a quarter or even and eighth of an inch. That may very well pop the electroplating. You would not want that. The other thing I wanted to mention is that I spent some time thinking about the life of the diamonds and how to protect them. I would not use a stone dry, especially when new. I use baby oil during most honing operations and use alcohol when I think some extra cleaning is in order. These stones will wear down eventually, but this is a slow process if you protect the diamonds with the oil and use light pressure. The stones will stay flat and the wear does not release fresh abrasive.

I move from the diamond stones to the ceramic stones. You only need two, the medium and the fine or super fine. The fine and super fine have the same abrasives. You have probably read that the fine and super fine remain flat and that they cannot be lapped. Not true. Just today, I found my super fine out of flat. I use a carborundum stone with baby oil to work it flat again. As with the diamond stones, I use baby oil for honing and alcohol occasionally to get some extra cleaning action. These stones wear but do not slurry up and release new abrasives.

For now, my process for a damaged bevel or for flattening is DMT X Course, DMT Fine, DMT XX Fine, Spyderco Medium, and Spyderco Fine. If the sharpening action of the DMT XX Fine changes as many have said it will, I may drop the Spyderco Medium from the process. For now, it is providing a more polished surface than the DMT XX Fine.

With the large number of blades I maintain, I have spent a lot of time in experimentation trying to get a proficient methodology in place that gives me consistent results. The 5 stones I am using now are really doing the job for me. If you want a mirror finish, the Spyderco Fine will give you that after it is broken in. I think the Spyderco Fine is 2000 grit. If you have a 8000 grit water stone or higher, finish a surface with that. Then, move the the Spyderco Fine and watch the polish emerge. This really speaks to the fact that grit size and density create confusion. Different kinds of stones on different steels do different things. I wish I could make this easy.

Sorry for the long post. It is a little complex. Grit size does not equate to honing finish. Different stones cut differently. Different steels have different honing requirements. OK, it gets real complex. : ) And, of course, there are many good stones available other than DMT and Spyderco. If you have those, just work with them and figure out for yourself what order you need to use them in to get the results you want.

Short version: Get your stones flat, protect the abrasives with a liquid during honing, and figure out for yourself what abrasive action is provided by each stone.

 

[elmeringalo]

Hi, which is the real grit of M, F and UF Spyderco stones? I read very different things about it.

 

[fsatsil]

Hi, which is the real grit of M, F and UF Spyderco stones? I read very different things about it.

There is no real grit rating for the Spyderco stones because of the way they are made. The best approximation I've seen for them is Medium=15micron, Fine=6micron, and UF=3micron.

 

[Obsessed with Edges]

There is no real grit rating for the Spyderco stones because of the way they are made. The best approximation I've seen for them is Medium=15micron, Fine=6micron, and UF=3micron.

Yeah, the Spyderco stones are each made with the exact same abrasive stock, which I think is approximately ~15-25µ in size (see quoted comments from Sal Glesser in thread linked below). Only the binders are different (for the brown/grey 'medium' hone), and surface finishing of the hones makes up the rest of the differences. The 'grit' approximations have to be made based on the apparent finish left on sharpened edges, and really have little/nothing to do with the actual size of the grit in the hones themselves. I've noticed the brown/grey 'medium' Spyderco fairly closely emulates the finish of something like an EF DMT (1200 mesh/9µ) most of the time, and the Fine and UF Spyderco hones are somewhere beyond that. The estimation given above is likely as close as any I've seen, but it'll always still be very subjective, and will vary based on the steels finished by them as well. More wear-resistant steels will effectively finish to a finer degree, because the abrasives won't cut them as deeply, leaving finer scratch patterns.

Quoted text below is from this thread on Spyderco's own forum --> http://www.spyderco.com/forumII/viewtopic.php?t=31188

"All of the ceramics use the same micron size (15-25). the different grits are created by different carriers, different firing techniques and diamond surface grinding.

sal"

"We've spent a great deal of time trying to determine grits for our stones. The manufacturer has also worked with us, to no avail. A guess seems to be best.

Most abrasives are measured by the grit size used in the matrix. Our ceramic doesn 't work that way. Grit size is constant.

We've tried to compare scratch patterns as Cliff mentioned and this is probably the closest, but nothing that we can say "This is blah blah". Then the Japanese water stones jump into the equation and suddenly there is whole new set of numbers.

So where we end up is:

Our diamonds are a 400 mesh (measureable). (600 on the Duckfoot)

Our gray stone is "medium". (Same material as fine but different carriers and heat treat).

Our fine stone is fine.

Our extra fine is a surface ground fine.



sal"

David

 

[Alberta Ed]

I wipe my DMTs down with BreakFree whenever they seem to be getting a bit slow, and leave them overnight. That seems to restore their efficiency. My 6" bench hones have lasted me 20+ years now and work as well as when new. I cherish a huge old Black Arkansas bench hone which I inherited from a great uincle cabinet maker. It's about 14" long (chipped on one corner); it produces a fabulous finishing edge on high carbon steels like 1095, 51200, Carbon V. Doesn't work so well on high alloy/carbide steels like S30V, though.

 

[Obsessed with Edges]

Diamond hones are by far the easiest to take care of. Use light pressure when sharpening (this is really the only thing affecting whether they hold their grit or not), and just clean them with some dish soap & water after each use, perhaps scrubbing with an old toothbrush. They'll be fine with such simple care, and will last a very long time. It's all I've ever done with my DMT hones, and they've never slowed down. Oil isn't needed on diamond hones, and DMT actually recommends against it. It won't harm the diamond, nickel substrate or steel plates, per se; but it just lends more opportunity for the oil to get gummy while collecting swarf and therefore clogs the hone, IF the oil isn't cleaned off regularly and thoroughly.

Some 'cheaper' diamond hones with an interrupted grinding surface (with 'holes') mounted over plastic have been known to separate from their plastic backing, due to oil being used on them which breaks down glue used to hold them together (I found this out in reading online reviews about certain 'inexpensive' diamond hones). I'm betting a more quality brand like DMT might not be affected as severely, but it's something to be aware of. I've sometimes tried a little mineral oil on my pocket DMT hones (Dia-Fold and Mini-Sharp hones), just to experiment with it's effect on feedback, but I've always cleaned it completely off after I'm done.

Some very coarse diamond hones can clog easily when sharpening low-end, soft stainless steels; the steel literally comes off the edge in ribbons (like Christmas tree 'tinsel'), and will clog the surface of very coarse diamond hones (XC and coarser). That's incentive to clean & scrub those hones frequently, even multiple times in one sharpening session, if grinding very heavy or large blades.


David