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I am looking into getting a set of diamond stones so I can start some serious sharpening. I am doing some now with sandpaper but I am starting to find aspects tedious and am looking at other options.

The thing that gets me is that I have been seeing two different styles.

There is, what I would call, your standard stone.

diamond block stone

And then you get stones that have the appearance like the zoomed in image below. Notice the cutting surface has spaces.

another diamond stone

While both of these images are from LeeValley tools I would like to point out that I am not trying to draw attention to the stones themselves. In the case of LeeValley both product pages mention chisels so in theory they are both capable of sharpening edge tools.

I am trying to figure out if there are any differences between the two that would make me want to choose one over the other.

Or perhaps it just boils down to price and opinion in which case the answer would be something along it doesn't matter.

  • I'm slowly transitioning to using diamond stones for my sharpening tasks. I started with sandpaper too, found it too messy and wasteful. I'd like to get rid of these dirty oil stones, but the funds need to clear first... – grfrazee Sep 17 '15 at 21:17
  • Any reason why you want to use diamond stones at all? Diamond has the advantage over lasting longer (since diamond is hard, but also expensive) over simple wet stones. It is not intrinsically "better" otherwise. These stones -- I just looked at Lee Valley's site, and I'm surprised -- are ultra brutal. They call 325 "coarse", 600 "fine", and 1200 "extra fine". For anything that isn't a gardening axe, I'd consider 600-800 coarse, 1200+ fine, and 6000-8000 extra fine. – Damon Sep 18 '15 at 8:36
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    Ah yes, that's more like it! Didn't see those. DMT is something I've actually used in the past, too... these are nice ones (only just, almost twice the price of a japanese wet stone). – Damon Sep 18 '15 at 11:24
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    @Damon If someone ever gets me a 50$ gift card for LeeValley I would be sarcastically thankful since then I could afford to buy a set of pencils. – Matt Sep 18 '15 at 11:29
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    @Damon, you can get a workable edge from 600, certainly good enough for rough planing tasks for example. Obviously you want to go higher than this for many things but there's an uncomfortable reality here: an edge sharpened to 4K and beyond will quickly degrade when working wood — within minutes of use, depending on species — to approximately the level of a 1k sharpen. – Graphus Sep 18 '15 at 14:49
8

I am trying to figure out if there are any differences between the two that would make me want to choose one over the other.

Or perhaps it just boils down to price and opinion in which case the answer would be something along it doesn't matter.

Yes, it mostly boils down to price. The continuous-surface diamond plates tend to be significantly more expensive with, honestly, no clear advantage.

If you just want to dip your toe into diamond sharpening I would recommend you get inexpensive diamond plates of the type you see everywhere. In the US they'll usually be less than $10 for a set of three, and currently there's a four-sided block with a plastic holder on Harbor Freight which is $9.99 (shown on the right below).
Inexpensive diamond hones
People using high-end diamond products from the likes of DMT can be horrified at these and assume they can't work properly, but the practical experience of a great many users argues otherwise. There's a lot written about how much flatter the name-brand plates are (which is undeniably true) but at the end of the day that tends to matter most to OCD types who obsess over that sort of thing.

Bottom line is this:
Are the inexpensive ones as good as the more expensive plates? No.
Can they be good enough to do the job? Yes.

To illustrate the point, I recently re-sharpened a 'rescue chisel' (bought some months ago covered in rust) using my old diamond plates. This was done just to confirm that a bare-bones sharpening system built around cheap diamond plates could be enough.

The chisel was previously sharpened with a convex/cambered bevel so first step was to re-grind the bevel flat, which took roughly seven minutes, including stops to check for square and adjust grinding pressure as needed. Then I worked up through the grits as you would normally do.

Inexpensive diamond sharpening 1
Inexpensive diamond sharpening 2

And finally stropped for final edge refinement. Not pictured was a final honing step but you can go straight to stropping from the fine plate, you just need to strop for longer to compensate (e.g. 40-50 strokes as opposed to 15-20, the difference of less than a minute).

Inexpensive diamond sharpening 3, stropping and results

Since the strop was homemade from scraps the total cost of the sharpening equipment used here was €8 (equivalent to approximately $9 at the time of purchase).

If you'd like to take this further I would still argue against buying the expensive plates. They're undeniably very good and seem to hold up well to use, but they're expensive compared to viable alternatives, e.g. oilstones, or steel plates charged with diamond paste.

If you're interested in more on the latter see this page from Bob Strawn, Overkillsharp™ Honing Method. If you source the diamond pastes directly from a Chinese supplier a full setup of five, even ten, plates can cost less than a quarter of a single DMT plate!

  • Harbour Frieght always scared me about the low prices but nothing stops me from trying them out. 10$ is easy to swallow over. I was worrying about buying multiple plates. Thanks. – Matt Sep 18 '15 at 11:22
  • @Matt, yeah I can understand the reticence — stuff that cheap can't be any good, right? But quite a few of the inexpensive things from HF are really quite decent and excellent value, e.g. their chisels and needle files. And anyone in the market for a scrub plane, their "no. 33" smoothing plane is a great starting point to make the cheapest one going, costing even less than a name-brand replacement iron! – Graphus Sep 18 '15 at 14:42
  • I always assume I'll get a week's worth of use out of a HF tool, and if I get more, I'm excited about it. I often do get more use out of them, so I'm frequently excited! ;) – FreeMan Sep 29 '15 at 19:46
7

I am trying to figure out if there are any differences between the two that would make me want to choose one over the other.

There is really only one significant difference I can see between the two examples you posted.

The diamond plates in your first example are solid plates with a consistent diamond grit across the entire surface. I own one of these types (fine grit, used for final honing) and it works well.

The second type, with the plastic circles, allow for swarf to accumulate in the plastic divots, which can lead to better cutting action and less clogging of the diamond grit. However, these have less diamond grit overall, so they will likely wear out faster.

In practice, I don't think one will really cut much faster than the other - at least, not noticeably for a hobbyist. If properly lubricated, either will work fine. I usually use water (or spit, if I don't feel like going to the tap). Paul Sellers uses window cleaning fluid for his diamond stones. A honing oil (light mineral oil) will work also, and I've seen that WD-40 works as well. Certain oils could eat away at the plastic circles, so beware if that's the type of stone you're using and check the manufacturer's recommendations.

  • I think you're right to caution that certain oils can eat away at the plastic. Mineral spirits (UK, white spirit) seems to have caused, or accelerated, the decay on the plastic bases of my plates and they've become brittle and cracked badly. – Graphus Sep 18 '15 at 7:16
6

The diamond stone with holes in the diamond surface will usher away the metal shaved off the blade and thus makes the sharpening process faster. It is also easier to clean up. However it is less suitable for pointy tools such as needles or awls as they could dig into the edges. For those tools continuous surface is better. For regular stuff like knives both kind of stones do a good job and is a matter of preference.

5

It seems the other answers so far have all been hobbyists who use their diamond stones occasionally, which is fine (though I may be wrong!), but I can speak from the perspective of using these stones in a commercial environment:

I work for a joinery shop with ~15 full time joiners. For our sharpening needs we have a Tormek grinding/honing wheel, plus a set of three DMT-style (unsure of actual make) diamond stones with the plastic circles like this one: http://www.buybrandtools.com/acatalog/DMT_Diamond_Whetstones_Set_6in.html?gclid=CJSGgvLjq8wCFQoTGwodckECMg This is a fantastic setup and I would recommend it to anybody, however I would actually recommend that if all you're sharpening is chisels (and no wider blades e.g. planes) then the Tormek system on its own is fantastic and all I typically do is grind the bevel and then hone on the leather wheel and I get a SUPER sharp edge.

In the past I also worked at a smaller shop with ~10 people and all we had was a single "fine" grade diamond stone of the same type (with plastic circles) and a honing angle guide to ensure the correct cutting angle.

I can tell you that with the high level of use in our workshop, and in my previous workshop, the fine grade stone (600 grit) with the plastic circles is absolutely adequate on its own to get a good working edge. The same stone was also used for 5+ years with minimal loss of effectiveness. If I were buying sharpening kit for my home shop and was on a tight budget, all I would buy would be one fine grade stone and a honing guide - the angle guide really helps to get the perfect angle for a good cutting edge with the right balance of sharpness and durability. I was more than able to get a razor sharp edge which easily shaves the hairs off of the back of your hand. In my current place of employment I don't think the finest grade of diamond stone really gets used, even though it is available - it takes too long, and the extra pay-off isn't worth it most of the time. To be clear a 600 grit stone will take you from a slightly chipped/damaged blade to a finished edge just fine. If you need to regrind the whole bevel on a large chisel you can do it, with a bit of work. If somebody asked me to do this on a finer stone I'd be reluctant just because the material removal is that much slower.

That's not to say that you won't get a sharper edge with a finer grit BUT bear in mind that the sharper you make the edge of a given blade, the less time it will last. If you're trying to (e.g.) get super-fine shavings with your plane then you may want to get finer grits but for most work, the edge you'll get from a 600 grit stone is more than adequate. I'd also note that a 600 grit diamond stone is not like using 600 grit sandpaper - since the stone is solid you can get much more even pressure on the blade etc. and you'll get a way better edge.

If you're going to be stropping the blade on canvas/leather etc. after honing then it's also not as crucial to get a really fine grit stone.

On the topic of the continuous stones vs. the ones with the plastic circles - I have used both and I think I prefer the plastic ones as I find I can get a smoother action going with them. As mentioned, the wear for a hobbyist on either type of stone should be a non-issue.

4

The more abrasive surface the stone has, the faster it will cut. Stones with less abrasive surface will probably be less expensive, but will not cut as fast (or as evenly).

This is probably one of those "Is it true, does it matter" type of questions. In real world use, it probably isn't a significant difference between the two. There may be a more significant difference between well made stones and poorly made ones. Having consistent grit sizes throughout the stone is important as you get down to finer grits.

Remember that you will need multiple grits to fully finish a blade. Personally, I use a coarse diamond stone for setting the bevel and grinding away larger amounts of metal, because the diamond stones don't get dished out. I prefer to use water stones (shapton specifically) to finish the edge.

2

The holes are there to stretch less diamond over more area. In power applications holes can help cooling, but that is not a factor in hand sharpening.

Diamond cuts faster than other abrasives.

I would get the non-hole stone because it will cut more metal per stroke than ones with holes. Your time is probably more valuable than the extra amount spent on the stone.

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