DMT Dia-Sharp Benchstones (D10E, D8EE)

Waterstones have been around for quite some time now, and have virtually replaced oilstones as the sharpening medium of choice.

Recently I tried two diamond encrusted benchstones from DMT, an extra fine (D10E) and an extra, extra fine (D8EE). The Extra Fine is rated at 9 microns, making it somewhat equivalent to a 1200 grit waterstone. The Extra, Extra Fine is rated at 3 micron, comparable to an 8000 grit waterstone.

In one sense these could be classified as waterstones, as they use water for lubrication. However, that's where the similarity between the two kinds of stones ends. Most of the affordably priced waterstones today are made of aluminum oxide, silicon carbide or chromium oxide abrasives. These abrasives wear down quite rapidly, and as they do, an uneven surface is created on the stone. Which is why you have to constantly flatten waterstones. Dia-Sharp stones, on the other hand, are made of 3/8" thick nickel coated steel plates covered with a continuous layer of industrial diamonds. Unlike the grit in waterstones, diamonds wear very slowly. On the Vickers Hardness Scale, diamonds are about eight times harder than aluminum oxide grit. Harder, more durable, lasts longer, more economical - you get the picture. You can read more about the monocrystalline diamonds used on DMT stones right here.

D10E (extra fine grit)

D8EE (Extra, extra fine grit)

The proof of the stone is in the finish. I used both stones to sharpen a rather ratty bench chisel that I had on hand. The Dia-Sharp stones cut noticeably quicker than equivalent grit waterstones. What I especially liked about the D10E stone was it's large 4" by 10" surface, which makes it ideal for sharpening wide plane blades. You can also use this stone for flattening any waterstone up to 2000 grit. I used it to flatten a 3000 grit waterstone, but the scratch pattern it left was much too coarse.

Original condition: back side

Original condition: bevel

The D8EE cut appreciably faster than my 8000 grit waterstone, but the finish it left wasn't quite as fine. However, I arrived at a usable edge sooner, which means I could get back to work sooner. I only made two dozen strokes on the D8EE stone; a bit more time on the stone might have resulted in a somewhat better finish. You can, of course, use the D8EE to flatten any waterstone in your sharpening arsenal. You don't need to pre-soak diamond stones as you do waterstones - spray them with water (DMT recommends adding a few drops of soap into the water) before, and during use. Afterwards, just wipe them dry. On the back of each stone are four rubber feet that help to keep the stones from sliding around on your work table as you use them.

Renewed back

Renewed bevel

The tow photos above show the results of about 2 minutes work on the D10E followed by 25 strokes on the D8EE.

For anyone who works in a production shop, I'd recommend diamond benchstones, simply because they get you from the sharpening station back to work sooner. And when you make your livelihood from woodworking, efficiency and productivity are what count. With these diamond stones you'll get a very sharp edge quicker than with a waterstone, and you don't have to concern your self with leveling the stones. Plus, you'll find that diamond stones have a longer life span than waterstones.

For hobbyist woodworkers, or those who lay awake at night unsure if their tools are as sharp as they could be, then waterstones are the way to go. Cutting action is slower, but you do, in my view, get a slightly better finish with an 8000 grit waterstone than with the D8EE.

Reviewed February 2011