The DMT Dia-Sharp 8 in is a continuous-surface diamond bench stone, 8 x 3 in, made in the USA in seven grits from Extra-Extra Coarse to Extra-Extra-Fine.
The diamond surface is one continuous sheet on a nickel-coated steel base, ground very flat. With no holes in it, small and pointed tools slide across without catching or gouging the stone, and it's big enough for most tools and knives. It's also good for flattening plane soles, plane irons and chisel backs. Four rubber feet hold it in place. Sharpen dry or with water; no oil is needed.
Extra-Extra Coarse (120 micron, 120 mesh) removes metal fastest and repairs damaged edges. Extra-Coarse (60 micron, 220 mesh) sharpens very dull edges quickly. Coarse (45 micron, 325 mesh) sharpens dull edges or refines after Extra-Coarse. Fine (25 micron, 600 mesh) refines a coarse edge or touches up a moderately dull one. Extra-Fine (9 micron, 1200 mesh) puts a very fine edge on a nearly sharp tool. Medium-Extra Fine (6 micron, 4000 mesh) and Extra-Extra-Fine (3 micron, 8000 mesh) finish and polish the edge.
DMT, short for Diamond Machining Technology, was founded in 1976 by aerospace engineers. It started out making grinding wheels, and its first hand sharpener was made from the center punched out of a diamond grinding wheel. A buyer at L.L. Bean tested an early sample and worked with DMT's engineers to refine it. Acme United bought DMT in 2016, and DMT is based in Marlborough, Massachusetts.
