hugh, if you were using a dentist drill set up, and the bits were flying out of the handpiece, the problem might have been the turbine. That is the nose cone on the NSK, and the collet on the angled handpiece. These tools are delicate and can be damaged when trying to force the bit through wood or simply being 'hamfisted'. For anyone using these tools, if your bit no longer stays in the nose cone or collet, the first thing to look at is replacing that part. On the NSK, it's a $200 part to replace.