Second-ranked Rory McIlroy also looked sure to have the weekend free when the Northern Irishman added a 71 to his first-round 78 for a five-over total of 149.
Hideki Matsuyama and Chez Reavie both shot the rounds of the day, posting seven-under 65s to move to five and four under respectively.
"Getting married kind of chills you out, and I don't want to put on too much of a show for her out there", he said on Friday, hinting at past outbursts on the golf course. "Yeah, it was a bit of a roller coaster".
Jason Day's struggles continued. "I was out of it. trying to stay out of the way of Rory".
With the top 60 and ties qualifying for the final rounds at Erin Hills, the cut appeared set to fall at one or two over par as the afternoon wave started their second rounds.
"If we get rain tomorrow and it gets wet and it plays soft, this place is going to get soft and you're going to have to be aggressive and you have to make a ton of birdies", Snedeker said.
The past six majors have been won by first-timers, and that cycle has a good chance to continue. That still didn't appear to be almost enough.
McIlroy has birdied three of his last four holes.
There's a requirement for survival at a U.S. Open, which happens to be golf's ultimate test. PGA Tour rookie Xander Schauffele didn't make a bogey at Erin Hills until his 27th hole, had his hiccup with a double bogey on the par-3 13th hole but still managed a 73.
Scheffler isn't the only amateur making waves at Erin Hills, with Cameron Champ two shots back of the lead at 5 under.
World number one Dustin Johnson led an unprecedented exodus of big guns at the 117th US Open on Friday as four players grabbed a share of the lead at the halfway stage.
Fleetwood was alongside Reed after a birdie on the first, but Casey tumbled down the leaderboard after following an opening birdie of his own with a triple-bogey on the third. I started missing some left and tried to correct it and missed a couple right.
QUOTEWORTHY: "I'm not here on the weekend, so it's unfortunate". Even just trying to take my medicine is very, very hard. It's a good eight in the end.
And the former Ryder Cup player then made it five birdies in succession - just one short of the US Open record equalled by Adam Hadwin on Thursday - by picking up shots on the first, second and third.
Only eight shots separate the leaders from the players who made the cut on the number.
The 25-year-old from Japan opened his U.S. Open with a 74 on Thursday, then rallied Friday to not only make the cut but to play himself into a tie for eighth heading into the weekend.
Day and McIlroy were left feeling pretty empty, as each had arrived to Wisconsin nearly a week ago with high expectations.
The four-way tie was the most after two rounds in a U.S. Open since Winged Foot in 1974, back when the names were more familiar for a major - Raymond Floyd, Arnold Palmer, Gary Player and Hale Irwin, who went on to win his first major. McIlroy could only take some optimism away from his finish. "You play 54 holes around here before the tournament, I felt really really comfortable".
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