The top-ranked Federer, beaten in last year's final at Melbourne Park by Rafael Nadal, hasn't lost to Hewitt since the Australian beat him in a Davis Cup match in the same Rod Laver Arena in late 2003.
The Swiss star has reached the semifinals or better here every year since winning the 2004 title, his first of three in Australia. He improved to 17-8 against Hewitt, and their 25 head-to-head matches is the most among active players.
Federer broke Hewitt's serve in the ninth game of the third set with a stinging cross-court forehand that left Hewitt standing in the middle of the court. Federer held service in his next game, setting up match point with an ace and clinching it with a service winner.
"When I saw the draw and saw Lleyton floating around, it's not something I like to see," Federer said.
As usual, Federer rose to the occasion.
"Hardly made any unforced errors," Federer said. For the record, he made 30 to go with his 49 winners.
"If there were some, they were at moments I can live with. I was really able to press on the offensive, serve well when I had to, and I moved well as well. Overall I'm extremely happy."
Hewitt agreed that Federer played "special" tennis.
"He hit the ball extremely clean, and I just couldn't get into his service games, which made it tough," Hewitt said.
The win advanced Federer to a quarterfinal against Nikolay Davydenko, who beat 2009 semifinalist Fernando Verdasco 6-2, 7-5, 4-6, 6-7 (5), 6-3 earlier Monday to extend his winning streak to 13.
In other matches, 2008 champion Novak Djokovic beat Poland's Lukasz Kubot 6-1, 6-2, 7-5 and Jo-Wilfried Tsonga of France, who lost to Djokovic in the 2008 final, beat Nicolas Almagro of Spain 6-3, 6-4, 4-6, 6-7 (6), 9-7.
Djokovic, who will play Tsonga in the quarterfinals, said he's playing well despite having a dry run at Grand Slam tournaments since his Melbourne Park victory.
"They are two different persons, physically I'm much stronger and able to get through the tough matches," the Serbian player said. "The 2008 Australian Open is by far the best tournament I ever played ... I believe I can play the same this year."
Nadal takes on Andy Murray and Andy Roddick plays Marin Cilin in quarterfinals on Tuesday. Comeback player Justine Henin takes on Nadia Petrova - Henin leads the head-to-head matchups 12-2 - and Maria Kirilenko plays Zheng in women's quarterfinals.
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