A lovely bit of kit and fairly easy to work with. You must have a tool to grip the gemstone with under water, then use the bead reamer with your other hand to gently work a bigger hole in the stone. Check the MOH scale of whatever gemstone you're working with beforehand. I have mobility issues and find this a lot easier than trying to work the bead with a non-battery operated reamer. Highly recommended.
This item is the first reamer I have bought that does the job. I have rsi of the hands (due to constant jewellery making) but this reamer requires very little pressure..also works to enlarge holes in pendants drilled too small. GREAT TOOL.