
and 14mm drill bits from the same company/seller. I used them to expand from 1/2 inch until I was the right size for my application, so I can't comment on penetration. , soft and carbon-rich medium character. The only thing I don't like is that the shank that attaches to the drill was plain and tubular, not hex/octagonal like other drills or a recessed part so have a good grip to allow the drill to slide.