Breakin in a DMT stone

[Douglas Brummett]

I gotta say, after picking up my first big diamond bench stone, I am somewhat less than impressed. I picked up an extra coarse (D11X). Right off the bat I knew it would need some amount of wearing in to do. So I grabbed a new 3/4" chisel and worked it over the stone. I added water periodically and did my best to work the entire stone. I noticed right off that the stone had some very coarse regions and lumps that would catch and deeply scratch the steel. After about 20 minutes I had worn in the middle of the stone, but the perimeter as well as a couple of spots on the stone are still more coarse than the middle. This is with me paying attention to hone over the whole stone.

As it is the stone is not uniform grit. It is fairly uniform in the middle of the stone but all bets are off on the perimeter and if you pass over one of the rough spots.

When I spoke to a rep at DMT he recommended that I clean the stone. That makes sense, it could have some buildup/clogging in the center. And he recommended to use a waterstone to try to even out the wear. So basically to bed in my diamond stone I need to waste away some waterstone Yeah, that makes great sense. I am going to give it a try, but if my opinion doesn't drastically improve my DMT is going back to the vendor.

IMO this is unacceptable performance for a new stone of this price. Am I wrong here? What other tips and tricks do you have for evenly wearing in a DMT Dia-sharp?

[Brent Smith]

Hi Douglas,

I've noticed over the last few years that the quality of the DMT stones is falling a bit short of what it was. The rep gave you good advise though. I had bought an extra coarse stone last year and found some of the same problems you're having, so I delegated it to flattening water stones (another can of worms, let's not get into it....my opinion, not the best flattening method). After using it for that for a couple of days I decided to try a plane blade back on it. I found that it did a great job at this point. So try a water stone, if you're not happy go for the refund.

[John Dykes]

I didn't have a grinder for a long time, and used sandpaper to cut initial bevels for various angles on plane blades and chisels. It was hard work, and I burned through a considerable amount of sandpaper.

I took a "step up" to a blue Shapton 320(?) - and still found it to be considerable work with constant flattening. I even tried a Norton 220... Thought sandpaper was easier...

Took another "step up" to a large DMT coarse \ x-coarse (blue\black) board. For the $100 I spent, I should have bought a grinder.... It worked pretty well initially, but seemed to wear out quick. Folks say that when new, it cuts faster than it should - then settles into a consistent rate (if that makes any sense). When it was new, and cut super fast, I was happy. At the "normal rate," it was (is) lots of work. And again, I think sandpaper is fastest and easiest. (I have an old post about it somewhere...)

I finally broke down and got the Woodcraft slow speed grinder on sale (it is currently on sale too). I've always enjoyed sharpening - love it for some reason (must be my ADHD!) - but hated re-establishing bevels. Love doing it on the grinder... I'm no grinder expert - and just get by - but it's a world of difference. It opens up the ability to quickly change angles on various blades. I love it. I am poor however, and haven't bought any upgraded wheels - mortal sin, yes, I know.

I use the DMT now only to flatten my Shaptons, and yes - I'm with Brent - I'm not in total agreement with the crowd who thinks the DMT is perfectly flat. But... I'm not a very good woodworker anyway!

What was the question???

[Douglas Brummett]

Brent, interesting. I heard that advice and just envisioned the diamond stone hardly changing and me wasting away a bunch of my waterstone. I will take my King 800 to it and see what happens.

John, good points all around. I have my doubts that the 220g will be coarse enough for flat lapping. Typically I use 80g 3X and then 220g w/d, so it seemed I could use the dmt instead of the w/d and save some trees/money. I think the 80g 3x is still the best bet for initial flattening.

FWIW I have a wetstone grinder and the woodcraft low speed 8in grinder. They are principally bevel tools, not lapping or honing tools. I can lap and hone using the wetstone grinder, but I prefer to use my stones and flat strop. The DMT is just the latest in my sharpening trials and tribulations. I figure that eventually I will find my favorite method in the mean time all paths lead to Rome. Meaning the end result is the same: sharp blades. The only difference is what your preference is.

[george wilson]

I haven't got new diamond stones,but did notice the little tiny lumps of diamond on a 3000 grit stone I bought for the Toolmaker's shop before I left. I remarked on that in another thread.

HOW COARSE is your stone? I don't know what D11X is. I wouldn't call 220 coarse. Is it 120? I'd say to take it back,myself.

[Douglas Brummett]

I haven't got new diamond stones,but did notice the little tiny lumps of diamond on a 3000 grit stone I bought for the Toolmaker's shop before I left. I remarked on that in another thread.

HOW COARSE is your stone? I wouldn't call 220 coarse. Is it 120? I'd say to take it back,myself.

Heck, DMT calls 220g xtra coarse. 120g is xx-coarse.

I am going to give it the benefit of the doubt and give it another half hour or so to correct it's attitude. Several people who have far more diamond experience than I do recommended to try the waterstone and also to keep working at it a bit longer.

[Joel Goodman]

I have the Duo (plastic) and also the Dia (on steel plate). I found the Duo more consistent but it's also an older stone. Anyone else notice a difference between the different versions of DMT?

[Douglas Brummett]

You mention age, is the grit the same? The finer grit stones seem to suffer this issue less as far as I can tell from my digging around the net.

[george wilson]

I'm getting more thankful all the time that I already have bought all this stuff!!!

[Douglas Brummett]

I'm getting more thankful all the time that I already have bought all this stuff!!!

Bah, that's funny. The more stuff I buy the more I feel like I am just running an elimination process. Some items turn out to be great. Others sit on the shelf abandoned. And those worthy are sold off to try something "better". Most items are functional for sharpening, but personal preference and conveniences come into play in the grand selection scheme.

[Ray Sheley]

Don't forget, if you work a stone like most of us the center get's twice the action as the edges. I tend to go back and forth when "trying to use the entire stone" which means that you are spending twice as much time in the center of the stone as for either of the edges, unless you are conscious of it and compensate for it.

[David Keller NC]

Doug - Like you, I bought the DMT coarse stone for flattening the backs of tools. My reasoning at the time is that the Norton 220 "water stone" (it isn't really - it's just a loosely bound carborundum) was way too friable - it needed flattening every 2 or 3 minutes when getting the back of a blade flat.

Here's my thought on the DMT duo - it was, as you noted, really coarse at first. However, after spending a few days removing a few thousandths off of the back of a Hock infill plane blade to go into a Norris, it's actually way too fine. I did clean it with a stiff bristle brush and comet, but that didn't seem to help any. My take on it is that the diamonds are just too brittle, and break down too quickly. The stone still works, but it's really not much better than my Norton 1000 grit stone, so I usually use that first and then progress up the grits. I've also noted that the DMT is not nearly flat enough to go from that stone to a flat 1000g waterstone.

For those reasons, I decided I didn't need another DMT. I have, however, found they're little credit-card sized diamond honers and the diamond slips to be very useful in re-shaping molding plane blades and carving tools.

My typical procedure now is to start the flattening process on the side of the wheel of my TorMek (only for an antique that's really bad), then go on to the Norton 1000g waterstone. One comment about the Norton - if you flatten this stone on 220g wet-dry stuck to a reference surface, I find that the stone's surface glazes and won't cut well (and this is with copious amounts of water flushing while I'm doing it). This is the one instace where I find the Norton "flattening stone" to be of use, as the surface it leaves behind on the 1000g is noticeably coarser and cuts much more quickly.

It's odd, because the 220g paper doesn't do that to the 4000g and 8000g stones - they're pretty much the same whether I use the Norton flattener or the wet/dry on a piece of granite.

[george wilson]

I wonder how many users know that you shouldn't bear down hard on a diamond stone? Diamonds are VERY brittle.

[Douglas Brummett]

I wonder how many users know that you shouldn't bear down hard on a diamond stone? Diamonds are VERY brittle.

Yep, feels like a fine line to walk. You gotta push hard enough to abrade the steel and yet not so hard as to fracture the diamonds. I am guessing that is isn't too incredibly common since DMT just touches on the subject in their manual.

Okay, so I worked over mine with some waterstones last night and did a borax scrub. It was time to clean the water tub anyhow, so it was a good opportunity to give the stones a few passes over the dmt. It did seem to calm the edges and the areas that were catching the tool. I worked the perimeter for another 10 minutes this morning. It does seem to be settling into uniformity, but it still isn't there yet.

[Terry Beadle]

I have a coarse/xtra-coarse DMT. I use it for flattening my water stones but only for a partial stage of the flattening.

Like the comments above, I found that the DMT had a breaking in period and it resulted in a rough and fine spots pattern on the stone. So I use the xtra-course stone with this splottchy pattern to initially flatten a water stone. Once it gets near flat, I switch to the next lower related stone to finish flattening. Also I continually pivot the DMT so that splotchy pattern will be most evenly applied.

I've also found that the course side ( blue ) is much more uniform than the xtra-course side, so I use it to tune the flatness for a final few strokes just before going to the next courser water stone. For example, if I were flattening my blue 3000 natural water stone, I would use the 1000 grit water stone for final flattening after initial work with the DMT.

All the above is not what I expected from the DMT. I thought, diamond is the hardest substance available. In theory, it should never be dulled by a water stone. Not true to me as a user. It's very useful but it will not stay as effective from day one to day 1000. Something is sure wearing and the most wear is that the diamond grit is gone in some areas of the stone. I say that with out a microscope to inspect and verify that but resolve that comment due to how it seems to work.

I think my next move is to buy one of those granite rectangle machinist plates and put some wet/dry sand paper on it. That seems to be the most reasonalbly priced solutions and reported great results.

Diamond is really good at some things but it's not a buy it once and forget it solution.