Twist drill bits are the most common type of drill bit, used for cutting wood, metal, plastic, PVC and more. The cutting edges on twist drill bits, called lands, can dull with regular use. Drilling with a dull bit not only takes longer but also creates more heat, which can damage your work piece and remove the temper from the bit. You can keep bits sharp by making a bench grinder sharpening jig. Using this jig, you can sharpen a twist bit in a couple of minutes.
Place one side of the piece of angle iron flat on the bench grinder's tool rest. The long axis of the angle iron should be in line with the grinding wheel, with the end of the angle iron parallel to the cutting edge of the grinding wheel. Clamp the angle iron into position on the tool rest.
Place a drill bit into the inside angle of the angle iron with the cutting tip facing the grinding wheel (the grinder should be turned off). Position the bit so that one of the two lands (cutting edges) of the bit is directly above the other. Ease the bit forward until the land makes contact with the cutting wheel. Loosen the tightening screw of the tool rest and adjust the angle so that the entire edge of the bottom land is parallel to the edge of the wheel. Tighten the screw to clamp the tool rest into position.
Back the bit away from the wheel and turn on the grinder. Keeping one land directly above the other, ease the bit forward until the land begins to grind on the wheel. Grind for a couple of seconds and then pull the bit away from the wheel. Inspect the land to see if the entire length of the land has been ground. If it needs a little more grinding, put it back into the jig and grind for a couple of seconds longer.
Rotate the bit 180 degrees and grind the opposite land in the same manner as the first.
Inspect the tip of the bit, checking to see if the length of the two lands are ground to equal length. If one land is shorter than the other, regrind the shorter land until the two lands are of equal length.
Avoid the urge to grind a land more than a couple of seconds. Excessive grinding can create enough heat to remove the temper from the steel, which will cause the bit to dull much quicker than normal.
When cutting with a grinding wheel, always wear safety glasses to protect your eyes from flying sparks.