The defending champion finally ran out a 6-7(7) 6-2 6-4 winner against the world number 65 on Centre Court, marching on in her quest to emulate Steffi Graf's Open era record of 22 grand slam singles titles.
Williams thought she had won the first set and was walking back to her chair after a McHale forehand was called long with the world number one 5-4 and 40-30 up. To her chagrin, however, a Hawkeye challenge showed the ball brushing the baseline.
McHale went on to win the game and force a tiebreak in which a rattled Williams made a string of errors, including two double faults, before burying a forehand into the net to lose the set.
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Furious as she sat down, she repeatedly hammered her racket into the ground in frustration before hurling it behind her.
"I was just really, really, really angry. I had a lot of chances," Williams told reporters after the match, adding that she would "definitely" be fined.
"I've cracked a number of rackets throughout my career. I've gotten fined a number of times for cracking rackets," she said. "I don't want to go too long without cracking a racket. You know, I'm on track. I try to crack a certain amount a year. I'm a little behind this year, so it was good."
The 34-year-old put the disappointment of the tiebreak behind her and showed the battling form that has won her six Wimbledon crowns to take the next two sets, closing out the two-and-a-half hour match with three aces.
In a classy final flourish, she autographed her bent and discarded racket for a fan as she walked off court.
(Reporting by Pravin Char, editing by Ed Osmond and Clare Lovell)
