Jordan Spieth opened up a two-shot lead heading into the weekend at the 146th Open Championship but Rory McIlroy, Ian Poulter, Richie Ramsay and Richard Bland were all within striking distance at Royal Birkdale.
Poulter was then at three under after a 70 alongside US Open champion Brooks Koepka and a shot clear of Scot Ramsay.
McIlroy's 68 moved him to one under and the 2014 champion had Bland, Canadian Austin Connelly and American Gary Woodland for company with just nine players under par.
Spieth birdied the first from five feet but dropped a shot on the third and when he got a flier over the back of the ninth green, he was in a five-way tie for the lead at four under.
What was to follow was as remarkable a run of golf as you will ever see as he chipped in for par on the tenth, holed a 35-footer on the 11th and almost made an ace on the 12th. He then went par-bogey but a mis-hit second on the par five 15th ended up 15 feet from the hole and he made an eagle for a three-shot lead.
An out-of-character missed putt from three feet on the 16th led to a bogey before the two-time Major champion parred his final two holes.
"I'd give myself a B grade today which is giving myself some credit," he said. "I thought that I didn't get everything out of yesterday's round and I got more than what I deserved today.
"I'm playing about where my score stands. I'll try and straighten it out off the tee a bit and with the long clubs for the next couple of days.
"I'd be lying if I didn't say I'm going to feel plenty of nerves as we start this weekend and throughout the weekend but we'll just be head down, to the game plan and believe in the form that we've been in."
Early in the day, Kuchar fell out of the overnight lead with a bogey on the second but chipped in from just off the front of the green on the third and holed a monster left-to-righter on the next to jump out into the solo lead.
A poor second shot on the eighth dropped Kuchar back but he took advantage of the 15th before dropping shots on the 16th and last.
Poulter began his round with 11 straight pars, including an excellent save from 35 feet on the ninth that brought a fist-pumping celebration and a rapturous response from the crowd.
A good tee-shot on the 12th was followed by an excellent putt that handed the 41 year old a share of the lead but a dropped shot on the 16th saw him sign for a 70.
Koepka made bogeys on the sixth and 13th in a 72.
Ramsay is no stranger to links golf and he was a picture of consistency in his level par 70, dropping a shot on the 13th but regaining it on the penultimate hole.
McIlroy had his irons absolutely dialled in on Friday, birdieing the first, third and sixth to turn in 31. Gutsy putts on the tenth and 11th and an excellent up-and-down on the 12th followed to save pars but he could not make it four in a row from eight feet on the 13th.
After putting his tee-shot a long way right on the 15th he was back at level par but a birdie on the 17th moved him into red figures.
When Bland birdied the second and fourth he was in a share of the lead but bogeys followed on the sixth and eighth, with a double on the 13th after taking a drop from an unplayable lie. The Englishman bounced back with a gain on the next but gave the shot back on the 15th.
Rafa Cabrera Bello, Joost Luiten and Alex Noren were in the group at level par.
