* Spieth sets pace with second-round 67
* His playing partner Day collapses on final hole
* Woods set to miss the cut after a 76 (Updates after Spieth cards 67, Woods a 76)
By Mark Lamport-Stokes
UNIVERSITY PLACE, Washington, June 19 (Reuters) - Masters champion Jordan Spieth sank an eight-foot birdie putt on his final hole, the par-three ninth, to seize the clubhouse lead in a dramatic U.S. Open second round at Chambers Bay on Friday.
While former world number one Tiger Woods was destined to miss only his sixth cut at a major after battling to a six-over 76, Spieth carded a 67 after watching playing partner Jason Day collapse because of dizziness off the ninth green.
Spieth, aiming to become the sixth player to win the Masters and U.S. Open in the same year and the first since Woods in 2002, posted a five-under total of 135 in the year's second major, which is being played for the first time in the Pacific Northwest.
South African Branden Grace was at four under after firing a 67 while co-leaders overnight, American Dustin Johnson and Swede Henrik Stenson, were among the day's late starters on the challenging links-style layout.
Australian Day, who has suffered from dizziness in the past, was immediately hooked up to an IV drip and helped to a waiting van after signing his card for a 70.
"He (Day) was fine, he didn't say much (in the scorer's hut," Spieth told reporters after a round that included six birdies, a bogey and a double at the tricky par-four 18th.
"He just signed his card and we told him to get some rest and water and whatnot."
Spieth, a double winner on the 2014-15 PGA Tour, was delighted to end his round with a birdie after the unusual delay on the ninth green where Day was attended by four medics.
"That was one of the better birdies I've ever made given all the situation," said the 21-year-old American. "Obviously there was some wait time in between, but I actually got somewhat of a read off Jason's putt and was able to knock it in.
"I struck the ball significantly better today with my approach shots. I hit my irons and wedges better today than yesterday, I also putted better today.
"I'm not quite putting myself in the same positions off the tee, so I've got to be a little more methodical. But if you shoot in the sixties at a U.S. Open you're going to be pleased."
Spieth birdied four of his first eight holes before running up a double at the 18th where he hit his drive and third shot into bunkers, then covered his homeward nine in one-under 35.
While Spieth mainly flourished on a hot day with gentle breezes, 14-times major champion Woods was at the opposite end of the leaderboard and certain to miss the cut.
A shadow of the player who dominated golf during the late 1990s and early 2000s, Woods mixed two birdies with eight bogeys as he slumped to a 16-over total with just one player in the field of 156, Darren Clarke at 17 over, faring worse.
"I hit a little bit better today, but again I made nothing (on the greens)," said Woods, who struggled to an opening 80 on Thursday to record the fourth-worst score of his career as a professional.
"I didn't make any putts the first two days; I hit it better today, hitting some spots where I could hit some putts; I made nothing." (Editing by Gene Cherry)