The Buckeyes sprinted out to a 16-3 lead on the strength of star big man Jared Sullinger, who had eight points in the opening sequence, including the first six, while taking advantage of a size and strength advantage inside.
Michigan responded with a 6-0 run, but Thomas brought that to an end with a jumper from just inside the three-point arc. Sullinger followed with a leaner in the lane for two, and Lenzelle Smith Jr. made one of two free throws to push the lead back to 12.
Wolverine guard Stu Douglass made a three – Michigan's only successful try from beyond the arc in 13 first-half tries – to cut it back to nine, but the Buckeyes ripped off nine of the next 11 to regain firm control of the contest.
Ohio State opened the second half with the first five points, a three-pointer by William Buford from the left corner and a pair of Sullinger free throws that pushed the Buckeyes' lead to a game-high 18 points.
The advantage reached 20 on a Craft three with 16:04 remaining, and the Wolverines never were closer than 16 again the rest of the afternoon.
The Buckeyes and Spartans will play at 3:30 Sunday afternoon in a rubber match from the season series.
Against the Wolverines, Sullinger finished with a game-high 24 points on 9 for 14 shooting while Thomas made 10 of 15 field goals – including 2 of 4 from beyond the arc – to finish with 22 points. Buford added 10 points and four rebounds.
Craft scored only six points but his contributions came on the other end and were obvious as he terrorized Trey Burke, Michigan's star freshman point guard, all day. Burke scored 30 points the night before in a quarterfinal win over Minnesota, but he managed only five against Craft. Burke was 1 for 11 from the field and charged with eight turnovers against just four assists. Burke missed all seven of his three-point attempts.
"Stopping a great player like him, especially with how he was feeling from yesterday, it was definitely a team effort tonight," Craft said. "Trying to not make it about me against him because that's not what it's about, our bigs did a great job hedging ball screens today and everyone else did a good job of zoning up and not giving easy baskets for the most part."
Tim Hardaway Jr. led Michigan with 13 points, but he also struggled from the field, going 3 for 10.
Michigan never led and finished with18 turnover and just seven assists. The Wolverines shot 30.9 percent (17 for 55) from the floor, including 4 for 25 (16 percent) from beyond the arc.
"This game definitely was about our defense," Ohio State head coach Thad Matta said. "I thought that we had great activity on the ball, off the ball. Our ball screen defense was good. Our bigs were extremely active. I thought we had great communication, challenged shots."
Ohio State kept the ball moving after establishing the inside game and finished 31 for 63 (49.2 percent) from the floor, including 5 for 14 from three-point range. The Buckeyes turned 13 offensive rebounds into 19 second-chance points and dominated in the paint with a 40-24 advantage in front of 18,451 fans at Bankers Life Fieldhouse.
"The ball was moving and we were able to maintain," Matta said. "We knew Michigan was going to run at us, and these guys countered. I thought the start to the second half was really, really big for us."
It all added up to send the Buckeyes to the Big Ten tournament final for the sixth time in eight years under Matta's tutelage.
"I just think it goes to show the type of coach that we have and his ability to have his teams ready to go and be successful at this point in the year," Craft said. "So with that said, it's definitely not going to be given to us tomorrow, so we need to come in and hopefully just try to continue to play our best basketball and see where it goes from there."