A new drill bit before being attached to the drill next to an old drill bit, worn out after its 50-hour run.

To dig deep beneath the ocean floor, the drillers on the JOIDES Resolution had to drill through some seriously hard rock. Compare a new drill bit to one that worked for 50 hours. On the old bit, the tungsten carbide nubs that do the cutting have worn flat, and many have been torn out. The core gauge, which shapes the sample core, is also worn and no longer round. The bedrock has even worn away at the steel body, making it a couple inches thinner. If it gets too small, it will drill a hole too narrow for the next bit to fit.

Every 50 hours the crew pulled up the entire drill string—some three miles worth of pipe and equipment—to replace the drill bit. Pulling up the gear, replacing the drill bit, and lowering the gear again takes about a day.

Compare the drill bits before and after use

A completely destroyed drill bit.