There are two different drilling types: full-drilling and half-drilling. Full drilling is a hole that goes all the way through a cultured pearl. This type of drilling is used for pearl necklaces, where the string must pass completely through the pearl. Half-drilled pearls are used for pearl earrings, rings, pendants, tie tacks, brooches, and other types of similar jewelry. The hole is drilled through half of the pearl, allowing the Akoya pearl to be mounted on the gold setting of the jewelry. The same system of drilling is used for other pearls as well as for Akoya pearls.
Drilling is extremely delicate work, as the Akoya pearl is drilled using two drill bits from each side for the complete hole. Drilling with one longer drill bit would risk damaging the nacre when it comes out the other side. One slip and the pearl can be completely destroyed.
Pearls with a single blemish on one side can be cut and then half-drilled in order to make them useful. For instance, for a pearl ring, the pearl may have had an original blemish on the side of the pearl that is attached to the ring. Instead of discarding this pearl, the blemish can be cut off the pearl, and then the half-drilled hole can be drilled on the cut side of the pearl. The pearl is attached on that side to the ring and there still remains a beautiful piece of unblemished pearl jewelry.