Core bits allow users to core small chunks of material out of larger slabs, but grinding through sheets or blocks of metal or stone can quickly dull the diamond grit on the end of the tool. Diamond core bits are reserved for the hardest ceramics -- such as granite or sapphire -- that shrug aside the efforts of other, less hard bits. However, harder materials mean more resistance and quicker wear. Sharpening a diamond core bit exposes new diamond and restores glazed bits to their full cutting capacity.
Raise the drill head to its resting position. Lock the head in place.
Place an aluminum oxide dressing stick -- also known as an Al203 stick -- underneath the drill. Clamp the dressing stick securely to the table.
Power on the drill and allow it to reach full speed.
Lower the drill until the bottom cutting surface of the core bit comes into contact with the dressing stick. Cut into the dressing stick as shallowly as possible, letting the diamond sink into the aluminum oxide but minimizing exposure to the side of the bit. Allow the bit to spin on the dressing stick for two or three seconds.
Raise the core bit away from the dressing stick. Drill into the dressing stick two or three more times in different locations.
Raise the drill to its resting position. Power off the drill.
Check the cutting surface for exposed diamond. Look for the glistening of newly freed grits. Run a finger along the diamond; sharpened core bits feel abrasive rather than glazed over. Drill into the dressing stick a few more times if necessary.