DMT extra extra coarse opinions?

[dan sherman]

Has anyone that has used, or owns one of these stones care to share what you thin of them?

They sound like the would be great for rough work, 120 Micron, flat to +- .001"

[george wilson]

I have all the grits these stones come in.My black plastic base diamond stone is the coarsest. it is good for rough work,and leaves a coarse finish,as expected. I don't use it all that often,as my tools don't get dull enough to warrant more than a touch up.

[Phil Harding]

I use mine mostly to flatten my waterstones.

-- Phil

[Mike Brady]

I question that degree of flatness. If you measured half a dozen you might find one close to that. If you only buy one.....well, you get what I mean.
I use mine for rehoned primary bevels and sometimes for waterstone flattening. I find the DMT X-Coarse to be handy, but not particularly fast cutting. I think you need something much coarser to regrind a bad edge; like 80 grit paper. Probably it's best use is flattening backs of plane blades and chisels, as the first cut.
Diamond stones are pretty expensive. I managed to buy mine through Amazon for about $60. I bought a med/fine Duosharp through them also. To be honest , I could live without them. When I don't need a waterstone-keen edge, they are easy to use and relatively tidy around the workbench. I use mineral spirits as a lubricant on them, which allows me to just wipe them down quickly and put them away.

[dan sherman]

I question that degree of flatness. If you measured half a dozen you might find one close to that. If you only buy one.....well, you get what I mean.


I had heard about the flatness issues with DMT stones, that was part of my reasoning for this thread, this stone runs almost twice what an extra course stone does $76 compared to $42, so maybe the extra cost went into making the stone flatter?

I was thinking this stone would be good for bulk material removal like re-establishing the primary bevel, Flattening backs, etc.

[george wilson]

If were talking about the all metal stones(I thought this was about the plastic base ones) I had to select among several to get the flattest one. Some aren't too flat.

[Mike Henderson]

I have the extra coarse as well as one other and use them for flattening my water stones and for working an edge with a bad nick.

Mike

[David Keller NC]

I had heard about the flatness issues with DMT stones, that was part of my reasoning for this thread, this stone runs almost twice what an extra course stone does $76 compared to $42, so maybe the extra cost went into making the stone flatter?

I was thinking this stone would be good for bulk material removal like re-establishing the primary bevel, Flattening backs, etc.

I don't understand the premise here - I checked Woodcraft, and the different grits are all exactly the same price in the Duo Sharp stones (the ceramic-backed ones with the perforated surface), and they're very close to identical in the Dia-Sharp stones (the continuous surfaced metal stones). But the price difference is substantial depending on what size you get - perhaps you were looking at two different sizes with two different grits?

I use the Duo-Sharp (the "perforated" surface) extra coarse as the initial step in flattening the backs of chisels and plane blades. It's quite fast, and doesn't run the risk of excessively dubbing the edge as sandpaper is prone to doing. However - if you use the kind of pressure that you'd use on a coarse waterstone or sandpaper, you will very quickly break down the diamond coating, and you'll be left with a "fine" stone that has a few larger particles that leave lots of scratches. In other words, a stone that's not a good "extra coarse", nor a good "fine". Because the diamonds are essentially a monolayer on the surface, you really cannot restore a stone like this that's worn. That's why it's not a very good idea to buy a used one of these off of sites like e-bay.

[Erwin Graween]

Hi.

I have the stone. The one without holes.
Mine is rally far from flat.

Not a problem for bevel, but you can not expect to flatten the back of something with it (dissapointed ...)

Hope it helps.

[dan sherman]

perhaps you were looking at two different sizes with two different grits?


same sizes

DMT D8XX 8-inch Dia-Sharp Bench Stone - Extra-Extra-Coarse (http://www.amazon.com/DMT-D8XX-8-inch-Dia-Sharp-Bench/dp/B000GLPCO2/ref=sr_1_1?ie=UTF8&s=hi&qid=1254675252&sr=8-1) $75.99

DMT D8X 8-Inch Dia-Sharp Continuous Diamond Extra-Coarse (http://www.amazon.com/DMT-D8X-Continuous-Diamond-Extra-Coarse/dp/B001DZOKNY/ref=sr_1_3?ie=UTF8&s=industrial&qid=1254675252&sr=8-3) $41.93

[David Keller NC]

The price difference still doesn't make sense - usually, the finer grit stones are more expensive, whether diamond, waterstone, oilstone or other. Might be worth a call to DMT - perhaps Amazon has an error on their website.

[dan sherman]

Might be worth a call to DMT - perhaps Amazon has an error on their website.

I plan on doing that Monday, because Amazon isn't the only place that lists the stone in the mid 80's.

sharpeningsupplies (http://www.sharpeningsupplies.com/8-2X-Diamond-Stone-P59C3.aspx) $84.95

[george wilson]

Actually,David,IIRC,the coarse ones cost more(I could be wrong) It could be that the larger size diamonds are harder to make.

[dan sherman]

Actually,David,IIRC,the coarse ones cost more(I could be wrong) It could be that the larger size diamonds are harder to make.

George, has it, It cost more, because the diamonds are bigger (talked with a rep).

[Mike Brady]

David , I agree with your observation that diamond stones (DMT) perform very differently after a dozen uses than they did during the first use. Everyone seems to agree with that. Some describe that process as "breaking in", but to me it is more like "breaking down". I have read several theories of why this might happen, and what to do, or not do, to avoid it. Some say to not press hard. Others offer a list of lubricants; while still others say to not use diamonds on softer steel. Considering all of the above, my newish X-coarse Dia-Sharp stone really struggles on A-2 planes irons. If the iron is thick, like on L-N planes, you are in for a long session of scubbing on that stone to get a nice primary bevel. The bottom line is that the X-coarse really is more of a medium grit like 150 or 180 in sandpaper terms. This happens to be a good grit to start chisel and plane iron back flattening, and to do it without the edge and corner dubbing that sandpaper on glass or granite seems to deliver. That is the best use for diamonds stones best use, in my opinion.

[David T Ross]

David,
I bought the extra-extra course stone a couple years back to flatten the back of a massive slick. It started out flat but wore unevenly even though I moved around on the stone and now it's less than flat. It still works great for flattening my water stones and taking out the occasional nick but I have to pay close attention. Ditto Mike's "breaking down" comment- it's not as aggressive as it started out, though it still removes a decent amount of material. Over all, because of the price, I'd hesitate to buy it again.

[Sam Takeuchi]

I have two DMT diamond stones, coarse and fine. They are not flat, and never was. I'll never buy anything DMT again.

Strangely, I picked up a cheapie double sided diamond stone at a home center for $30 last year. Not even certain of the brand, but this 8" one is dead flat on both sides. Serving me well flattening other stones.

[Brian Simmons]

I am not at all pleased with the XX Coarse. In my usage (in flattening plane blades and soles) it leaves deep scratches, even in light usage. I could not remove these scratches. I went through a complete sequence to 8000 grit and got a mirror finish that still had scratches in it. I called DMT and all they said was, in effect, "Well that's how it works". I have done several planes and consider mine well broken in.