A monster drill chewed through bedrock underneath the Port Authority Bus Terminal Thursday and sent tons of rock crashing to a cavern floor - the last bit of drilling to extend the No. 7 train. City and MTA officials in hard hats cheered as the second of two machines - named Emma and Georgina after Mayor Bloomberg's daughters - finished their year-long run from 34th St. and 11th Ave. The city is paying for the $2.1 billion project. "We talk about these big projects. This is one that we're actually doing, and we're doing it on-time, on budget," Bloomberg said.