Carbide drill bit broke on first dive. When I asked about this, I was told that I would probably be sinking and moving at the same time, creating too much torque on the drill, and that I would have to sink and move in two passes. Since then I've bought almost all of my bits through Precisionbits.com. They have almost the same wide range of Yonico bits, and the bits are just as good but a lot cheaper.