Over the years, I've bought these from numerous suppliers. Every one I have allows the drill bit to slip inside the countersink portion. I'll set the depth for a 1 1/4" screw and after boring a hole or two, the bit will slip up into the countersink. This, I know, is a minor irritation, but I'm getting older and crankier. Does anyone know of a supplier that sells them that locks the depth up tight?