I'm wondering how to string 1 mm leather lace or suede into cultured freshwater pearls. I've seen a design that the pearls are between 10-12 mm. Do they drill them or use a reamer and do it one by one? Thanks!
It is recommended to use a pearl reamer to enlarge pearl holes, and yes, one at a time.
You can also use a fine drill bit fitted to a rotary tool or Foredom® flexshaft. Using caution, drill each pearl halfway, from one direction, then from the other direction working all the way through the hole, while holding the pearl in a shallow dish of water. The water will keep the drill bit cool, flush the water out of the hole as you are enlarging it and keep the dust to a minimum. Also consider wearing a dust mask to prevent inhaling any airborne dust created when drilling. There are a couple of other solutions you may enjoy:
Use a smaller diameter leather cord or hemp that fits through the drill hole a little easier
Use Swarovski crystal pearls, which have larger, consistent drill holes
The larger holes will not only allow you to use thicker stringing materials, you can also easily pass beading wire through each pearl numerous times for multi-strand designs