Things You'll Need
Bench grinder with adjustable tool rest
6-inch piece of angle iron, 2 inches wide
Twist bits are the most commonly used drill bits in home-improvement projects, because they are so versatile. A twist drill bit can be used to drill into wood, plastic, metal, tile, PVC pipe and many other building materials. Using a twist bit on a variety of materials can dull the cutting edge on the tip of the bit, known as the land. You can build a simple homemade sharpener that sharpens twist bits on a bench grinder.
Turn off the bench grinder. Lift the spark shield up and out of the way.
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Align the long edge of the piece of angle iron so that it is perpendicular to the face of the bench grinder's cutting wheel, resting on the tool rest. Position the leading edge of the angle iron so it is about 1/2 inch away from the face of the wheel. Clamp the angle iron to the tool rest with a C-clamp.
Place a twist drill bit into the inside edge of the angle iron. Position the bit so that one land -- the cutting edge on the tip -- is directly above the other. Push the bit forward until it touches the stationary grinding wheel.
Loosen the wing nut on the tool rest. Adjust the angle of the tool rest until the bottom land on the drill bit is flat against the face of the grinding wheel. Tighten the wing nut to lock it in place.
Slide the drill bit down the angle iron about an inch. Start the bench grinder. Verify that one land is still directly above the other, then ease the bit forward until it begins grinding the lower of the two lands. Keep the bit against the wheel for no more than 2-3 seconds, then ease the bit away and inspect the newly ground land. The edge of the land should be ground evenly and completely.
Flip the bit over and repeat the process, grinding the other land in the same manner.
Inspect both lands to make sure they are of equal length. If one land is shorter than the other, regrind the shorter land until both lands are the same length, to ensure the bit will cut evenly and smoothly.
When sharpening drill bits, always wear a long-sleeved shirt and safety glasses, to protect against flying sparks.