Diamonds may be a girl’s best friend but some would call them a woodworker’s best buddy. It’s been over a century since DeBeers cornered the diamond market creating an artificial shortage of gem-quality diamonds that exists today. But that shortage and the resulting high prices of what are, in actuality, rather common gems spawned a diamond manufacturing industry in the mid-fifties that is still growing rapidly today. The ubiquity of diamond abrasives is a direct result of that enterprise – virtually all of the diamonds available for sharpening are manufactured, not mined.
Diamonds are a near-perfect abrasive medium, being the sharp particles of the hardest material known. DMT is a leader in the diamond sharpening industry with a large catalog of diamond honing devices, plates and gadgets. Diamonds are stuck down to a steel plate with nickel plating holding them in place. The plating process sometimes includes a “clump” of “rogue” diamonds. These consist of an extra diamond particle or two piggybacking onto one that’s properly stuck down. This creates a larger than desired grain on the surface that will cause large scratches on the tool being honed. These rogue diamonds are why diamond “stones” need breaking in. You can use them hard with blades that you can risk having large scratches in, or you can gently rub two diamond plates together under running water to knock off the rogues and create a uniformly graded surface. I found this break-in requirement the only “con” to the diamond plates that I tested.
Diamonds are also available as loose, graded-grains, though more commonly they’re mixed into a paste. Norton’s diamond paste honing kit comes with four syringes with 5grams each of different grit-size diamond paste, color-coded so you know which size is which at a glance. The kit includes four pieces of MDF to be used as the embeddable substrate, one for each grit size. I found these best for polishing but be careful to avoid grit contamination. Store each block in its own plastic bag between uses to keep them clean.
That’s it for the Abrasive Personalities posts. Most sharpening abrasives are covered under the four categories. If you feel your knowledge and experience may be of benefit to others, please post a comment.