Kelly Gibson (67), Joel Kribel (67), James Driscoll (70), Chris Tidland (68), Zoran Zorkic (67) and overnight leader Larry Rinker (72) share third place at 5-under-par 137.
Buha opened with a bogey but quickly reclaimed the lost stroke with a pair of birdies over his next three holes. It was his move on the back nine that gave Buha the 36-hole lead.
He drained a 15-foot birdie putt at the 10th and followed with a 20-footer for birdie at the next hole. He holed a long birdie putt on the 12th and made it four in a row with a 15-footer at the par-5 13th.
The 27-year-old dropped a shot at the par-3 14th when his ball plugged into a greenside bunker but it was not enough to drop Buha from the top spot on the leaderboard.
'I kept it in play and it helps to be hitting it long out here,' said Buha, who has finished in the top six in his last two starts. 'It really helps to know the humps and bumps around this track.'
Gage, who was alone in second after the first round, struggled early with a pair of bogeys on the front side at the TPC at Wakefield Plantation. He tallied two birdies over a three-hole stretch to claim second place.
'It's tough. The greens are getting crunchy,' said Gage, who missed only one fairway on Friday. 'Putting was tough. There's a lot of shots where I had to think about hitting up the hill.'
Steven Alker is alone in ninth place at 4-under-par 138.
The 36-hole cut fell at 1-over-par 143 and 61 players qualified for weekend action.
Full-field scores from the SAS Carolina Classic