The Australian world number one and Wimbledon champion withstood a barrage of swinging left-handed serves and powerfully-clubbed groundstrokes from Dick Norman before advancing 7-6, 3-6, 6-4 in a shade over two hours.
Hewitt's reward is a place in the quarter-finals of the 800,000-euro grasscourt event, where he will play France's Sebastien Grosjean, a 6-1, 6-4 winner over Todd Reid.
"He (Norman) serves so well... it helps when you are coming down from 6ft 8ins (2.032 metres) I guess," Hewitt said. "I don't think anyone at Wimbledon is going to serve any better than that.
"That was a different kind of match out there... he made it very hard to find a rhythm."
Hewitt was joined in the last eight by second seed Andre Agassi, No. 3 Andy Roddick and Britain's three-times runner-up Tim Henman.
Agassi, looking unamused at being put on a dewy grasscourt in the early evening, destroyed fellow former Wimbledon champion Richard Krajicek in just 48 minutes.
Lashing winners all over the court, Agassi crushed the Dutchman 6-1, 6-2 and next faces Xavier Malisse.
By contrast, Roddick and Henman were made to toil hard for their wins.
Roddick tussled with Briton Greg Rusedski on Centre Court before prevailing 6-3, 4-6, 6-4, threatening Rusedski's service speed record with a 147 miles (236.6 km) per hour delivery.
That serve was officially clocked as the second fastest ever, just a touch slower than Rusedski's world record 149-mph (239.8 km) serve hit in Indian Wells five years ago.
Roddick will face fellow American Taylor Dent in the last eight.
"This is the most comfortable I have felt on grass thus far in my career," Roddick said. "I thought I played pretty well all the way through. I got here a little early and I think that has been beneficial."
Henman again made life difficult for himself, dropping the first set against little-known Frenchman Cyril Saulnier before winning 6-7, 6-3, 6-3.
He next plays another Frenchman Anthony Dupuis.
"Perhaps I've been a little unsure on serve at times... but you only have to look at what is happening out there now to see how well the guys are returning now," Henman said.
"But it is the sign of a good player that you can win when things aren't going so well. I am coming through some difficult situations."
Hewitt was made to scrap all the way in his match against the 2.03-metre tall Norman, an imposing figure at the best of times who is even more of an obstacle on a slick grass court.
After nicking the opening set on a tiebreak he was powerless to prevent the towering Belgian from charging through the second to square matters at Queen's Club.
With clouds gathering overhead, the two seemed inseparable in the third set as it lurched towards what looked like an inevitable tiebreak.
At 4-4, Norman threw everything at Hewitt, forcing the top seed to fight off six break points.
A cheeky lob over the enormous Norman clinched Hewitt the game and five points later the match was his when the Belgian's backhand rolled along the turf into the net.
