First-round leader Olin Browne (76) and 2002 champion Sergio Garcia (74) shared sixth place at minus-1 on the Plantation Course at Kapalua Resort.
This event is reserved for PGA Tour winners from the 2005 season. Four of those winners -- Tiger Woods, Phil Mickelson, Retief Goosen and Padraig Harrington -- qualified, but elected to skip the week.
Like Thursday, players faced high winds on Friday. Winds gusted well over 30 m.p.h., which pushed scores well over par. The field compiled an average score of 75.51, the highest single round average for this tournament since it moved to Kapalua.
'I hit driver down No. 9. I didn't have the best lie and I didn't have maybe the best swing at it, but I hit it pretty good. I hit it like 150 yards and that was a 2-iron,' said Appleby about the strong winds. 'Sometimes you're just guessing how many clubs you think you need to add to the shot versus the yardage. That's really what it is, guessing the right amount of wind and hoping that you pull it off. It's not a science when it gets like that out there.'
Browne was never able to get anything going. After a birdie on the par-5 fifth, he bogeyed four of the next five holes to drop off the pace. He played the final eight holes at even par with two birdies and two bogeys.
Appleby, who had never previously led this event after the second round, was steady over his opening nine holes. He tripped to a bogey on the second to slip to minus-1, but settled in with seven straight pars to remain there.
The Australian collected a birdie on the par-4 10th to grab a share of the lead at minus-2. Appleby parred his next three holes and then sank a 15-foot birdie putt at the 14th to grab a one-shot lead.
Appleby stretched that lead to two strokes as his pitch to the par-5 15th rolled within 2 feet of the cup to set up a birdie that moved him to 4 under.
At the last, Appleby's drive found a hazard to the left of the fairway. After a drop, his third shot came up short and right of the green. He chipped to about 12 feet, but two-putted for bogey and his lead dropped to one.
'I like the wind. Australia is a pretty windy place, but certainly nothing like this,' said Appleby. 'I haven't seen the weekend forecast, but I'd say if anyone got to double figures (under par) that would be excellent golf.'
Campbell opened with four pars, then dropped two shots in his next three holes to tumble to plus-1. He got those strokes back with birdies on nine and 11.
The New Zealander sank an 8-foot birdie putt on the 15th and got to 3 under with a birdie at 17. However, he also bogeyed the last to end at minus-2.
Furyk dropped shots on the second and seventh to fall to plus-1. He picked up birdies on eight, 12 and 14 to get within two of Appleby.
'Its a tough wind, but at Kapalua and here in Hawaii you're going to see a lot of strong winds. I wouldn't call it a normal day, but its not out of the ordinary,' Furyk said. 'I didn't have a lot of putts that went in today, but overall it was a good solid day and hopefully they'll go in on the weekend.'
Toms bogeyed each of his first two holes, before getting a shot back at the fourth. He faltered to another bogey on the ninth. Around the turn, Toms collected consecutive birdies from the 14th to finish at minus-2.
Singh was 3 over on his opening nine with a double bogey on the fifth and a bogey on No. 8. The world's No. 2 player birdied the 15th and 18th to get back within two of Appleby.
Jason Bohn carded the low round of the day as he shot a 3-under 70, which included four birdies over his final five holes. He stands at even-par 146 and shares eighth place with Bart Bryant (72) and Wes Short (73).
Mark Calcavecchia, Lucas Glover, Geoff Ogilvy and Vaughn Taylor are one stroke further back at plus-1.