i also learnt the hard way when drilling holes for pins in the wedge, if using fragile material drill the hole before tapering.
i used turquoise and the first one cracked when drilling. Second one i drilled at full thickness with now issue, then tapered.
With fragile scales, just back it up on a piece of wood and also put some masking tape on bath sides of each scale where you will drill. This helps stop chipping where the drill bit goes through. i use a coping saw for all my scale work {no power saw} and never have issues. Actually seems easier on the famed hard stuff like G10, and on softer materials, just go slow and let the saw teeth do the work.
Patience is the key.
Adam