DMT diamond sharpening: continuous or interrupted stones?

[maximus83]

I'm curious among those who use DMT sharpening stones: have you tried both the interrupted surface (those with the metallic surface on the stone with recessed holes to catch the sharpening residue) and the continuous surface stones, and what do you see as the pros and cons between the two types?

I currently have 2 of the 10" duosharp stones (EC/C and EF/F). These seems to work great in general, I love how they work. But one drawback I've noted with the interrupted surfaces: it's hard to sharpen portions of your blade right up to the VERY edge of the stone (because part of the metal wraps around the edge/corner, which keeps you from sharpening right up to the edge). What this means is, depending on the design of your blade, sometimes it's very hard or impossible to get that last little bit of your blade sharp right near the handle, since you can't go right up to the edge of the stone.

I would be interested to hear if anyone else has observed this issue, and if you've found effective ways to work around it with the interrupted duosharp stones (or if you've decided to switch over to the continuous stones to get away from having part of the stone covered with those metal coverings).

 

[Jason B.]

Continuous plates feel more like a stone with a constant drag on the sharpened bevel and a smoother scratch pattern. I prefer them.

About the stone not getting all the way to the ricasso, what knife were you sharpening?

 

[Talley1013]

I use the continuous DMT and they work great for me.

 

[Magnaminous_G]

I will weigh in on this to dispel a common misconception before anyone even mentions it: The holes in the Duosharp stones are *not* there to save money by using less diamonds (the common misconception), they are there because they make the stones somewhat faster (which I can attest to, having used both). That said, both are fantastic. So before anyone even mentions, please don't think that you are getting "more stone" with the Diasharps (uninterrupted); that's not why they are different and that's not why one has a continuous surface and one doesn't. I prefer the duosharps because they are faster. But I also like the diasharps, too.

If there is one disadvantage of the Duosharps, it is that very fine points (sushi knives, fish hooks, etc.) get caught in the holes. But for knife sharpening, the holes will not ever be an issue. Both stones are precision flat and top quality. Enjoy!

 

[bgentry]

So before anyone even mentions, please don't think that you are getting "more stone" with the Diasharps (uninterrupted); that's not why they are different and that's not why one has a continuous surface and one doesn't.

I don't claim any experience or expertise with the DMT stones. But what you've said above is counter-intuitive at best, and defies physics at worst. If a duosharp and a diasharp both have equal surface area (say 8" x 3"), and one has roughly half of it's surface *not* coated in diamonds, how can both have equal amounts of cutting surface?

I could understand if you're just saying that the duosharp lets the blade glide more easily and makes it faster for *you* to sharpen a blade. If that's it, then I get it. If you're claiming they have the same amount of abrasive or cutting power, then I'm not understanding.

I'm honestly interested in your reasoning and reply. I hope this doesn't come off in a bad way, as it's not meant to.

Brian.

 

[Obsessed with Edges]

I'm also skeptical of the interrupted being 'faster' than the continuous-surface hones. The difference in cutting speed is very apparent with smaller hones, especially, where total surface area of real abrasive is of paramount value. I use Dia-Folds (interrupted) and DMT's 'credit card' hones (continuous) quite a bit, and that 'tiny' credit card hone takes a much more aggressive bite, for it's size, than the Dia-Fold. I'm not knocking the Dia-Folds; I do like all of DMT's products. But, when it comes down to cutting speed, surface area that's actually covered in abrasive makes the bigger difference. I know I keep wishing for DMT to make a continuous-surface Dia-Fold line, for this very reason.

The 'holes' on the interrupted surface hones might play more into cutting speed IF one is generating an awful lot of swarf (or slurry, if using it to lap another stone). In that case, the holes play a role in helping to clear the surface of swarf and slow the loading up of the abrasive. But if generating heavy swarf or slurry, simply using the hone with a wetted surface, or periodically rinsing the hone, make the so-called 'advantage' of the holes less of a factor.

 

[maximus83]

So I guess something I'm confused about on the interrupted DMT's: What's really the point of them? They seem to cost a lot more than the continuous, but a visible different between them is that the continuous "stones" are actually solid steels with impregnated diamonds throughout. Whereas the interrupted stones have the steel SURFACES with the recessed holes, which supposedly catch the residue reducing "loading."

Here's a pasted description of the 2 approaches from the DMT site. I really don't KNOW if this is just marketing hype, or if it really works. But the CLAIM of DMT supports what Magnanimous-G is saying, which is that the purpose of the interrupted surface is to sharpen more aggressively (=="faster" results). This COULD be true I suppose, as the interrupted stones cost more and clearly are harder to manufacture. I assume they made these stones this way for a reason, and people do buy them as I did. Whether they really make a difference, hard to say as I haven't compared the 2 approaches side by side. That's why I was hoping some here could give me tips from hands-on experience.

Here's the DMT descriptions:

Interrupted Diamond
Our signature polka-dot pattern where the holes are slightly recessed in order to collect metal fines removed during sharpening. This unique to DMT feature prevents loading. Ideal for sharpening, honing and deburring.

Continuous Diamond
Made with the same consistently sized preferred Monocrystalline diamond as our 'polka-dot' interrupted surface products but performs with slightly less aggressiveness. Well suited for small contact areas and pointed tools as well as sharpening, honing and deburring.

 

[unit]

The holes can cause problems with very small blades, or blades with substantial curvature at the tip. Basically, any time the scale of the curvature on the knife approaches the scale of the holes in the hone...you run a higher risk of trapping your work into the holes just like the swarf they hope to trap.

The only advantage anyone has ever voiced to me for the holes is the provide a trap for swarf. I do not want to sound like a snob, but I believe that a "best" procedure would be one that aims to eradicate swarf before it pools in the holes.

 

[Magnaminous_G]

I don't claim any experience or expertise with the DMT stones.

Try them then, you'll have a better understanding.

But what you've said above is counter-intuitive at best, and defies physics at worst. If a duosharp and a diasharp both have equal surface area (say 8" x 3"), and one has roughly half of it's surface *not* coated in diamonds, how can both have equal amounts of cutting surface?

They don't have equal amounts of cutting surface... which is why I never said that. Read someone's post carefully before asking them to clarify things they didn't even say.

I'm honestly interested in your reasoning and reply.

DMT explains it thoroughly themselves, as someone above quoted from their site. Google.

 

[Obsessed with Edges]

The continuous surface hones are not diamond 'throughout' the entire plate. They too, are just surface coated with diamond (albeit, more of it). There's no advantage to having diamond throughout, as these hones aren't designed to break down (like waterstones) to expose 'fresh' abrasive. It's just a steel plate, coated with nickel substrate, and then surfaced in diamond abrasive.

 

[maximus83]

Here's an interesting online review of the duosharp stones that shows a handy diagram of how the nickel bed on the surface of the duosharp stones is impregnated with the diamonds, while below the nickel bed is solid steel, and of course the yellow part of the 'stone' is just a plastic material. Clearly these things are more complex and would take more steps to manufacture than the continuous stones, but that does not prove by itself that they work better or worse. For now, mine are working well, but I am going to keep my eyes open and keep reading about this.

http://www.onlinetoolreviews.com/reviews/dmtw250fcnb.htm

Edited to add: David I hadn't seen your post yet when i just posted this, but it looks like your comment is in line with the diagram and comments provided by the online reviewer about the construction.

Also, it just occurred to me why the duosharps cost so much more (doh, I didn't think of this earlier ). It's because the duosharps have the interrupted surface and diamond layers not only on both sides (which I assume the continuous ones do as well), but the duos ALSO have 2 DIFFERENT grits impregnated onto a single stone.

 

[Jason B.]

The holes are for collecting swarf nothing more.

My experience with many DMT products has led me to the conclusion that the duo sharp plates cutting faster is all in your head.


And I don't work for DMT but I will claim to be a expert on the products and their uses.

 

[maximus83]

My experience with many DMT products has led me to the conclusion that the duo sharp plates cutting faster is all in your head.
.

So basically in your opinion, the duosharps don't necessarily sharpen better OR worse, but they just cost more and the "interrupted" surface isn't worth the extra cost?

 

[unit]

The holes are for collecting swarf nothing more.

My experience with many DMT products has led me to the conclusion that the duo sharp plates cutting faster is all in your head.


And I don't work for DMT but I will claim to be a expert on the products and their uses.

I will argue with you on that

If you relax certain expectations in the name of speed, the holes will allow you to grind faster because you will eliminate the time spent rinsing swarf off the hone.

 

[Lagrangian]

I tend to prefer the continuous surface diamond stones. In my (limited) experience, they give a more consistent and flatter grind. For my knives with curved bellies, I could feel the edge going over the holes. I think this is due to three effects:

1. Because the surface is not uniform, sometimes the knife edge will be in contact with more surface area, and sometimes less. This creates variation in friction. I might be feeling this.

2. Because the blade has a belly, the curvature can slightly poke into holes. As the curve rides in and out of holes, the knife angle changes very slightly. I think this is also a possibility.

3. The edge of the holes may wear out faster over long term use. As a result, the stone might be losing a small amount of flatness at the hole edges. Not sure about this one (just a guess on my part), but if 2. is true, it would partly explain why the hole edges receive more stress/wear.

Sincerely,
--Lagrangian

P.S. btw, I'm using a guided sharpening system.

 

[unit]

So basically in your opinion, the duosharps don't necessarily sharpen better OR worse, but they just cost more and the "interrupted" surface isn't worth the extra cost?

Where are you finding them for extra cost? They cost less everywhere I have been. I have examples of both interrupted and continuous, but greatly prefer the continuous and would recommend spending extra to get them for those willing to spend more for better tools.

Edit to clarify: For someone that is not obsessing over results, "better" tool might be defined differently.

 

[Obsessed with Edges]

Here's an interesting online review of the duosharp stones that shows a handy diagram of how the nickel bed on the surface of the duosharp stones is impregnated with the diamonds, while below the nickel bed is solid steel, and of course the yellow part of the 'stone' is just a plastic material. Clearly these things are more complex and would take more steps to manufacture than the continuous stones, but that does not prove by itself that they work better or worse. For now, mine are working well, but I am going to keep my eyes open and keep reading about this.

http://www.onlinetoolreviews.com/reviews/dmtw250fcnb.htm

Edited to add: David I hadn't seen your post yet when i just posted this, but it looks like your comment is in line with the diagram and comments provided by the online reviewer about the construction.

Also, it just occurred to me why the duosharps cost so much more (doh, I didn't think of this earlier ). It's because the duosharps have the interrupted surface and diamond layers not only on both sides (which I assume the continuous ones do as well), but the duos ALSO have 2 DIFFERENT grits impregnated onto a single stone.

If I'm not mistaken, I think DMT also certifies the Duo-Sharp bench hones (interrupted) to be perfectly flat, within tight tolerances (not so with the Dia-Sharps). This is more useful for those using them to lap/flatten other stones (where slurry is an issue, also), AND also to woodworkers, who need to have a perfectly flat surface for sharpening chisels and plane blades. So, in a nutshell, I can see why the Duo-Sharps cost more to make, but I doubt it has much to do with cutting speed alone (as compared to the continuous surface hones).

Edit:
Regarding the woodworking angle, the C/F Duo-Sharp I have, actually came in a box with an 'endorsement' by Scott Phillips (his 'Signature Series', as labelled on the box). He's the host of a popular woodworking program on PBS. I've also seen him use these on his program, as described earlier (for chisels & plane blades).

 

[Jason B.]

I will argue with you on that

If you relax certain expectations in the name of speed, the holes will allow you to grind faster because you will eliminate the time spent rinsing swarf off the hone.

Two words, soapy water

 

[maximus83]

Where are you finding them for extra cost? They cost less everywhere I have been. I have examples of both interrupted and continuous, but greatly prefer the continuous and would recommend spending extra to get them for those willing to spend more for better tools.

Well for instance at a large online retailer starting with "A", the 8" duo's cost a good 20% higher on the average than the continuous stones. Also at KnifeCenter, which a lot of us here use, the same-size and same-grit duos tend to cost a LOT higher than the equivalent continuous stones (for instance, $78.95 for an 8" EF/C duo, versus $48.95 for various grits of the 8" continuous). Clearly they are more. Not a deal-breaker in itself--I agree you want to get whatever you think does the best job for you. However, my curiosity was on WHY the duo's were costing more. My guess is the extra manufacturing required for the interrupted surface, the different grits on each side of the stone, and as David said, the extra attention paid to tolerances. Those 3 items may be why the duo's that I have seen tend to cost a bit higher than the same-size continuous stones.

 

[MJF]

I really like my diasharps, but they definitely aren't perfectly flat. You may be onto something here obsessed. Sometimes I feel like I'm bumping over road bumps when I sharpen on them. Also, anybody else had a problem with rust on theirs?