A mandoline is composed of a very sharp blade that is mounted neatly within a block of wood, piece of plastic or metal. It provides precision cutting for vegetables and fruit. The blade of the mandoline is extremely sharp, but will dull with heavy usage. It is possible to send the blade to a professional for sharpening, but using a sharpening stone, or whetstone, is a more cost-effective way of restoring your blade to its former glory.
Put on gloves to protect your hands from being cut when handling the blades of the mandoline.
Use the screwdriver to remove the blade that you want to sharpen. You may need to disassemble the whole unit, or simply remove the specific blade. Refer to your mandoline's instructions to do this, as each one is manufactured differently. However, serated blades or jullienne blades cannot be sharpened with the whestone.
Read the instructions that accompany your sharpening stone. Some stones require lubrication with water or oil.
Place the sharpening stone horizontal, on a flat surface and steady it with your dominant hand. Hold the mandoline blade in the other, making sure that the blade is facing away from you.
Position the blade of the mandoline at the correct angle for sharpening. A 20 degree angle is appropriate for a mandoline blade. If the angle is too great then it will dull the blade, while a shallow angle will take too much off the bevel.
Push the stone across the blade firmly. It will make a sharp, slicing sound when you do this. Stroke the blade quickly with the stone.
Repeat the quick stroking motion to sharpen the blade for about five minutes. You can test that it is sharp again by cutting a vegetable. Then, rinse the blade under cold running water to remove shards of debris from the sharpening process.
Put the mandoline back together by replacing the blade and fastening the screws. Give it a wiggle before you cut anything to make sure it is secure.