Max Knives SP43 — Credit-card size diamond sharpener, 300 grit

Overview

The SP43 is a diamond sharpener cut to the size of a bank card: 8,3 cm by 5,2 cm, 1,5 mm thick. It slides into a wallet, a bag pocket or a tray in a toolbox, which means it ends up where you actually need it rather than on a workshop bench. The diamond-coated face works at 300 grit, so a few passes are enough to give back some bite to a blade that has been working all week.

What 300 grit really means

Grit is the key to everything in sharpening. A low grit such as 300 removes metal: it rescues a rolled edge, rebuilds a bevel that has hit something hard, redraws a blunt cutting edge. A high grit only polishes what is already straight. The order never reverses: you start with the coarsest grit the job needs, then refine. And a sharp edge is a safety matter, not just a comfort one, because a blunt knife slides across the material instead of biting into it.

Technical specifications

Credit-card format: 8,3 cm long by 5,2 cm wide, 1,5 mm thick. Abrasive face coated with diamond, 300 grit. That 1,5 mm keeps the plate rigid enough to be laid flat on a table and thin enough not to bulge a wallet or a jacket pocket. The flat format works either resting on a worktop, with the blade drawn across it, or held in the hand for a quick touch-up away from home.

Care

After use, rinse the surface under clean water to flush out the metal particles taken off the blade, then wipe it and let it dry before putting the plate away. A diamond abrasive asks for nothing else: it is never flattened and never resharpened. Wipe the freshly sharpened blade as well, since a new, keen edge is always more sensitive to moisture than one rounded off by weeks of use.