Tiger four clear at halfway stage

Tiger Woods showed why he is the ultimate grinder, posting a two-under 70 on Friday to ward off a host of challengers and seize control in the second round of the 91st PGA Championship.

Padraig Harrington, who shot 68 Thursday, hung in there, letting it be known that he doesn't plan on letting Woods too far out of his sight.

The two-time Open champion shot a one-over 73 to finish three-under on 141.

'I'm a little bit disappointed with the finish. I struggled in the middle of the round,' Harrington said.

Harrington birdied the par-three, 210-yard fourth hole to join Woods and three others in a tie for the lead.

He then used a superb second shot to birdie No 9 and get to five under.

Harrington parred the next hole to move into a tie with Woods, who made a bogey on the hole.

Woods took a four-shot clubhouse lead on a day of subdued scoring for the rest of the field Friday after the winds kicked up in the 7.5 million dollar event at the Hazeltine National Golf Club.

'It was a tough day all around,' Woods said. 'The wind was blustery. It was hard to be aggressive because you didn't want to run it past the hole.

'I just plod along see what happens. I got off to a poor start today but hung in there.'

With a win at Hazeltine, the world number one would tie Walter Hagen and Jack Nicklaus for most wins in PGA Championship history with five and claim his 15th career major, three shy of the all-time record set by Nicklaus.

A handful of players even joined Woods for the lead throughout Friday's round but they all eventually fell by the wayside as he turned a four-way tie on the front nine into a one-man show.

'We are all feeling the pressure,' Woods said. 'It is a major. If you are not feeling the pressure you shouldn't be playing.'

A number of big names remained in the hunt, including defending champion Padraig Harrington, US Open champion Lucas Glover, two-time PGA Championship winner Vijay Singh, England's Ross Fisher and Australian Brendan Jones all at three-under 141.

Woods moved to seven-under 137 and managed to extend his lead on the back nine despite posting three bogeys Friday after a bogey-free five-under 67 in the opening round.

Woods had back-to-back birdies on the front, rolling in a 15-foot putt on No 6 and a five footer on the seventh to get to six-under. That enabled him to regain sole possession of the lead.

On the back nine, Woods posted three consecutive birdies at holes 14, 15 and 16. He could have gone lower but just missed the eagle putt on the par-4 352-yard 14th.

Woods did not compete in the 2008 PGA Championship after having surgery on his left knee missing a chance to defend the title he won in 2007.

Scores were not as low in the second round as the first, with the wind picking up throughout the day.

England's Fisher, who shot a 68, also flirted with the lead on the back nine but had back-to-back bogeys to finish his round.

Rory McIlroy and Graeme McDowell will be around for the weekend finishing on level par and one over respectively.

Darren Clarke missed out finishing on ten over.