How to Check the Sharpness of Cutting Tool Edges

Using Your Hands

• 1

  Use your thumb to test the sharpness of a blade by placing your thumb pad at a minimal 15 degree angle to the blade, then slowly and carefully moving it down the blade. If your thumb pad catches on the blade, sharpening may be needed. If the cutting edge feels smooth, you have a sharp blade. Gentleness of touch is needed for this method. Do not press hard against the blade as you do not want to break the skin. A sharp blade will slice your skin easily. This method works best for fine-cutting tools such as scissors or hunting knives. You can always use a potato as a substitute for your thumb pad.

• 2

  Use your thumbnail to test a blade. Do this if your nails are long enough to make a cutting surface. Carefully press into the tip of your thumbnail at a 30 degree angle. Apply minimal pressure as to not cut the nail and go directly into the tip of the thumb and into your skin. If the cutting edge slips over the surface, it may need sharpening. If it starts to cut into the nail, stop applying pressure as you have a sharp blade.

• 3

  Use the hairs on your hand and arm to test blade sharpness for very sharp blades. Move the blade at a 30-degree angle down the arm against your hairs, but not touching the skin. If the hairs are not cut, the blade may need finishing. Be careful not to press against the skin with this method.

Other Methods to Check Sharpness

• 4

  Hold a piece of paper with one edge at a 30-degree angle with the cutting edge. Move the cutting edge across the edge of the paper. If the paper slices then the blade is sharp. If the cutting edge slips away, the blade may need sharpening.

• 5

  Use an old paintbrush to test sharpness by attempting to cut one of the bristles with your cutting edge. If the cutting edge does not slice through the bristle easily, you may need to sharpen your blade.

• 6

  Hold the cutting edge in front of you with the instrument perpendicular to a light source. Burrs in the blade will become evident as a glimmer of light on the cutting edge surface. This requires no cutting, only a keen eye to detect imperfections on your blade.