Las Vegas - Webb Simpson, seeking his first PGA Tour win since his 2012 US Open triumph, fired an eight-under 63 on Friday to take a four-shot halfway lead in the Shriners' Hospitals Open.
Webb had nine birdies and one bogey at TPC Summerlin, where his 15-under total of 127 put him four shots in front of a group of five players.
American JJ Henry, who held the first-round lead with a sparkling 60, carded an even-par 71 to join the bunch on 131, which also included Australian John Senden (66) and Americans Jeff Overton (68), Chesson Hadley (66) and Jason Bohn (64).
The defending champion in the $6 million event, Ryan Moore, matched Simpson for the low round of the day with a 63 that put him tied for seventh on 132 with Scotland's Russell Knox, who posted a 65.
"I hit a couple of loose shots today, but just really managed to make putts and take advantage of the holes that you have to make birdie on," Simpson said.
He has hit 32 of 36 greens in regulation over the first two rounds, and averaged just 1.53 putts per green.
Henry followed up his course-record effort of Thursday with an even-par round that featured four birdies and four bogeys.
Hadley, the winner of the Web.com Tour Championship who is making only his fourth PGA Tour start -- his second as a tour member -- had eight birdies and three bogeys in his five-under round.
"It's been a fantastic start to the week, and to have a chance going into the weekend is awesome," Hadley said. "(I'm) just looking to manage the nerves tomorrow and just realize it's just golf, and let's just go have some fun."
Although Simpson didn't post a win in 2013, he did qualify for the Tour Championship for the third straight year. His five top-10 finishes included a playoff loss to Northern Ireland's Graeme McDowell at the Heritage.
A final-round 63 vaulted him to fourth in the season-ending Tour Championship.
"I haven't won this year, but my one goal every year is to get better, and I felt like I got better," Simpson said.
The tournament is the second in the US PGA Tour's new-look 2013-2014 program.
Six tournaments are scheduled before January, offering FedEx Cup playoff points and a coveted Masters berth to the winner.
Leading second-round scores on Friday in the $6 million PGA Tour Shriners' Hospitals Open (USA unless noted, par-71)
127 - Webb Simpson 64-63
131 - John Senden (AUS) 65-66, Jeff Overton 63-68, Chesson Hadley 65-66, JJ Henry 60-71, Jason Bohn 67-64
132 - Ryan Moore 69-63, Russell Knox (SCO) 67-65
133 - Luke Guthrie 69-64, Stephen Ames (CAN) 65-68, Brian Stuard 68-65, Ryo Ishikawa (JPN) 67-66
134 - Brendan Steele 67-67, Daniel Summerhays 66-68, Brian Davis (ENG) 68-66, Morgan Hoffmann 67-67, Noh Seung-Yul (KOR) 69-65, Freddie Jacobson (SWE) 67-67
135 - Kevin Stadler 70-65, Carl Pettersson (SWE) 68-67, Jhonattan Vegas (VEN) 68-67, Brice Garnett 67-68, Brendon Todd 67-68, James Driscoll 63-72, Jonathan Byrd 63-72, Greg Chalmers (AUS) 67-68, Andrew Svoboda 68-67