Miami - South Korean Im Sung-Jae, aiming to parlay his Web.com tour dominance to PGA Tour success, shared the Honda Classic halfway lead with American Keith Mitchell on Friday.

Im, 20, fired a six-under par 64 on the Champion course at PGA National in Palm Beach Gardens, Florida, for a 36-hole total of six-under par 134.

He was tied atop the leaderboard with Mitchell, who posted a 66, with 2009 US Open champion Lucas Glover a shot back on 135 after a 69.

Im, who won twice and led the money list all season in dominating the developmental Web.com tour last season, birdied three of his first four holes and three of his final six on the way, his six-under effort tied for best round of the day.

"All the shots that I wanted to hit turned out the way I wanted," said Im, who hit five approach shots to within 12 feet of the pin.

"So it led to a lot of birdies, and I was able to convert a lot of my birdie opportunities. I think that's what led to a successful round today."

Canadian Adam Svensson also posted a 64 to land on 136, sharing fourth place with eight other players in a group that included 2018 PGA Tour Player of the Year Brooks Koepka (69), New Zealand's Danny Lee (67) and Sweden's Freddie Jacobson (67).

A total of 42 players were within five shots of the lead.

Defending champion Justin Thomas made the cut on the number with a four-over par 74 for a two-over total.

Im, the youngest of the US tour's rookies this season, went off in the first group of the day at 6:45 a.m. and made a quick move with birdies at the second third and fourth holes.

He would add three more before his lone bogey of the day at 16, and he drilled a 25-foot birdie putt at the 18th to cap his round.

Mitchell had five birdies and a bogey in his four-under effort, and after three missed cuts on the tour's West Coast Swing was delighted to be playing on the Bermuda grass greens of Florida.

"I grew up on Bermuda. I know how to putt it," he said. "I know how to read it. It's definitely helped a lot."

Thomas's hopes of a repeat title on the Jack Nicklaus-designed course faded with his four-over effort, during which he struggled with a "dead arm" as well as his concentration.

Thomas, who felt a stinging sensation in his right arm when his nine-iron scraped a tree on a shot on Thursday, said the arm still didn't feel right.

"Just feels like it kind of needs to get popped," he said. "Just doesn't have a lot of strength."

Leading second-round scores on Friday in the PGA Tour Honda Classic at PGA National in Palm Beach Gardens, Florida (USA unless noted, par-70)

134 - Im Sung-jae (KOR) 70-64, Keith Mitchell 68-66

135 - Lucas Glover 66-69

136 - Freddie Jacobson (SWE) 69-67, Adam Svensson (CAN) 72-64, Lee Kyoung-hoon (KOR) 67-69, Kang Sung (KOR) 68-68, Danny Lee (NZL) 69-67, Ryan Armour 68-68, Brooks Koepka 67-69, Wyndham Clark 69-67, Adam Schenk 67-69

137 - Roberto Castro 67-70, Cameron Tringale 69-68, Sergio Garcia (ESP) 67-70, Peter Malnati 69-68, Julián Etulain (ARG) 67-70, Jhonattan Vegas (VEN) 64-73, Charl Schwartzel (RSA) 67-70, Anirban Lahiri (IND) 67-70, Ben Silverman (CAN) 66-71