| Pearls are extremely difficult to drill without the right tools. You need to drill from either side or you will likely crack the nacre, and without the right drilling device it is very difficult to hit exact opposing sides.
It can be quite difficult to find someone in your area that has a drill as well, as very few jewelers would ever have one. I may suggest finding someone with a used one they are willing to sell. We replace ours approximately every other year, and we just sold one for half our cost (they run about $1200 new for the good ones). You can also find some lower-end machines in the $800 range, new.
If the pearl is half-holed it is likely drilled to a .8, and most strands (unless the pearls are large) are drilled to a .6mm. This means if you drill a half-drill completely through, it will likely slide over the knots (not very pretty.
If a whole strand of pearls are drilled large, you can actually string them, but you will simply need a larger gauge of thread. The knots may appear to be a bit larger than normal, however. |