The American golfer David Toms made the most of ideal scoring conditions after a lengthy weather delay to go seven shots ahead of the field in record-equalling style at the Colonial Invitational in Texas.
Co-leader overnight with compatriot Chez Reavie, the red-hot Toms birdied four of the last eight holes for a second successive eight-under-par 62 at Colonial Country Club.
The 44-year-old, who was beaten in a playoff for the Players Championship last week, matched the PGA Tour record for the lowest 36-hole start with a 16-under total of 124.
Fellow American Pat Perez set the same mark after the first two rounds of the 2009 Bob Hope Classic.
Australians Steve Bowditch and John Senden were tied for second at nine under with South Korean Charlie Wi and American Mark Wilson.
The cut fell at one-under 139 with former major winners Trevor Immelman, Angel Cabrera, Vijay Singh, David Duval, Ben Curtis and John Daly among those failing to advance.