Sam Burns avoided the late meltdown that cost him in the first round of the U.S. Open. He had a 65 and has a one-shot lead at Oakmont.

Sam Burns is a birdie machine at Oakmont, a label not many expected at this U.S. Open. By avoiding another sloppy finish, Burns posted a 5-under 65 on Friday and set the target for the late starters — and let Scottie Scheffler know the mountain he faced.

Victor Perez capped a nice second-day rally with a tournament highlight — the first U.S. Open ace at Oakmont since 1983. Perez hit a 7-iron on the sixth hole, a 192-yard par 3. Perez ended up shooting an even-par 70 on Friday despite an early triple bogey.

U.S. Open at Oakmont is testing the world's best golfers like few tournaments do. Here's how the cut line works at golf's toughest major.

If scores hold after the second round of the U.S. Open on Friday—and obviously they won't—the cut line is projected to claim anybody shooting worse than three over par.

Two rounds of the U.S. Open are (almost) in the books, and it has been as difficult as advertised so far. The vast majority of the field shot over par in the first two days, with only a handful of players ending Friday under par.