"We shape our tools and afterwards our tools shape us"

Posted: May 19, 2011

DMT 8" Dia-Sharp Continuous Diamond Bench Stones

Disappointing ...

Available from Amazon (prices are approximate)
     Extra-extra-course (120 grit) $70
     Coarse (325 grit) $40
     Fine (600 grit) $40
     Extra-fine (1200 grit) $60
     Extra-extra-fine (8000 grit) $70

I've tried a host of sharpening solutions for chisels and plane irons over the last few years. WorkSharp, Tormek, Scary-Sharp, etc. So far, I've been less than thrilled with the results of the powered systems. And while Scary-Sharp has given good results, it's a little pricey for all that sandpaper and I don't like the metal dust it produces. And my arms get tired ...

I've been considering going old school and getting waterstones to use with my Veritas jig. But I don't like the fact that they wear down and that I might have to keep flattening them all the time.

The DMT Dia-Sharp bench stones seemed to be a good idea. Shaped and used like a waterstone, they're actually nickel-coated steel plates with one surface impregnated with tiny diamonds in the nickel layer. Whereas the abrasive in traditional sharpening stones breaks away and exposes fresh, sharp abrasive, these diamonds form an extremely durable and permanent abrasive surface that should last quite a long time. DMT uses high-quality monocrystaline diamonds vs the cheaper products that utilize less-expensive polycrystaline diamonds. Polycrystaline diamonds are much easier to fracture, an abrasive plate with polycrystaline diamonds will wear out far more quickly.

The stones comes in several grits. I purchased three: The "coarse" 325 grit, "fine" 600 grit, and "extra-extra fine" 8000-grit. I was really torn on whether to get the 1200 grit stone, but the price was running up quickly. And since there was already such a huge gap from 1200 to 8000, I thought it wouldn't matter.

Like a waterstone, Dia-Sharp "stones" use water for lubrication and to wash away the steel "swarf" being ground off the tool. Unlike a waterstone, the water is not being used to also wash away broken-off abrasive grains since the diamonds don't release. DMT provides small stick-on rubber feet to help keep the stones from sliding around in all that water, but I found I preferred to put the stones on some Bench Dog Bench Cookies.

In actual use, the Dia-Sharp stones didn't live up to my expectations. While they initially cut quite well, they very quickly seemed to lose their abrasiveness. This was especially true of the "fine" stone, after one chisel I wasn't sure if it was cutting at all. Compared to Scary-sharp, the results weren't quite as good and it was actually quite a bit more work.

Looks like it's time to cave in and order some waterstones.


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