Williams, whose three world ranking titles last season elevated him to third in the world rankings, will oppose Matthew Stevens who had eliminated the defending champion, John Higgins, 9-7 in Friday's semi-final.
Hendry, five times UK Champion, made breaks of 80, 64 and 120 in leading 4-1 but did not score in the next two frames, in which Williams had runs of 77 and 92.
The Welsh left-hander missed a straight black on 26-0 in the closing frame of the afternoon, but Hendry immediately put a straight pink on the near jaw of a middle pocket and lost the frame to Williams' 72. "At 4-1 down I hadn't done that much wrong. I just had to fight hard to get back in the match," Williams said.
Breaks also told the story of the first three frames of the evening: 45 and 33 from Hendry to lead 5-4; 53 from Williams to level; 68 from Hendry to lead 6-5. Heading for 7-5 though, Hendry lost ideal black-ball position in potting the penultimate red. Even after failing to sink the black he was still in the driving seat until he grossly underhit what should have been a snooker for Williams, but instead let him in for a winning 33 and 6-6.
"That knocked me sideways," Hendry said. From 53-0 behind Hendry tenaciously got himself into a position to regain the lead but, having potted a difficult last red to a middle pocket, sent a routine black wide. "I don't think it's the pressure with Stephen, it's his concentration," Williams observed.
Williams went 7-6 ahead and, with Hendry thoroughly demoralised, seized victory with frame winning breaks of 75 and 89.
Beaten 9-8 by Higgins after leading him 6-2 in their Grand Prix final at Preston last month, Williams did not strike much form in his early matches at Bournemouth, even though he won them comfortably. Not until his recovery from two down, with three to play to beat Jimmy White in the last 16 did he start to function on full power.
"Earlier in the tournament I was looking for obstacles which weren't there until I decided to attack," he said. As Stevens shares a similar philosophy it should be a fast-moving final.
Stevens started his sojourn in Bournemouth even more uncertainly, trailing Joe Perry, who beat Steve Davis at The Crucible last spring, 7-2 and 8- 4 before coming through 9-8. The win released new confidence and energy which was still flowing through him when he out-played Ronnie O'Sullivan 9-3 in their quarter-final.
Victories over O'Sullivan, Williams and Higgins gave him his first major, the Regal Scottish Masters, eight weeks ago. His first ranking title today would be another significant milestone.Reuse content