Dear Jane: The best drills for pearls have been the flat drills that
look more like the old wood drill that are shaped like a spear
(auger). These do not cake and make clean holes.
Most of these are reversible (double sided so you have two pointed
ends on each end)
We find that the drills from Japan are the best. You can buy an
adapter chuck to fit most hand pieces (so that you can use the small
size drills). The adapter chuck is very cheap about $4.00 to 8.00
depends where you buy.
A dremel motor tool with high speed unto 20,000 rpm can be very
reasonable and you have inexpensive Drill stands for the dremel type
motor tools. Drill holder and vices are a good investment and you
get your money back pretty soon.