Australian number one Tomic won the day’s second singles 6-3 7-6(2) 6-7(4) 6-4 but he looked out on his feet towards the end after being rocked on his heels by the dogged Evans.
World number three Andy Murray had given the hosts a dream start as they bid for their first Davis Cup final spot since 1978, playing sublimely to thrash teenager Thanasi Kokkinakis 6-3 6-0 6-3 in front of a packed house in Glasgow.
The winners will face Belgium or Argentina in the final.
Scot Murray, 28, has been the mainstay of Britain’s rise from the lower levels of the Davis Cup pyramid in the last four years, and is likely to play Saturday’s crucial doubles rubber.
It was always on the cards that the tie would be poised at 1-1 after Friday’s play, especially with surprise pick Evans, ranked down at 300, playing against world number 23 Tomic.
After being initially outclassed and falling two sets behind, Evans dug deep, breaking Tomic’s serve at 3-5 in the third when the Australian served for the match and eventually clinching a tiebreak when Tomic volleyed wide.
Both players were staggering after some gruelling rallies on the slow indoor court in the fourth and Tomic was left gasping when he again failed to serve out the match at 5-2.
At 5-4, however, with Australian veteran Lleyton Hewitt pumping his fist courtside, Tomic held his nerve and claimed victory when Evans sent a backhand wide.
“There was a big expectation on Bernie to win and the weight of it all was grinding him down into the court, but that’s Davis Cup!” Wally Masur, captaining Australia as they aim for a first final in 12 years, said.
With Murray favourite to win his singles on Sunday the tie could now hinge on the Saturday’s doubles.
Murray earned a crucial point with brother Jamie, a U.S. Open doubles runner-up last week, in the quarter-final against France, and the brothers may be let loose against Hewitt and big-serving Sam Groth on Saturday.
After Murray’s longer-than-expected rest before the tie after a fourth round defeat at the U.S. Open, and the ease at which he beat Kokkinakis, the Scot is ready to work overtime.
“It isn’t my decision. It’s up to the captain to decide that. Obviously, now I have the option to be picked because that match was quick. We’ll talk about it this evening,” he said.
Murray’s demolition of Kokkinakis took his Davis Cup singles record to 24-2.
(Writing by Martyn Herman in London, Editing by Alan Baldwin and Ken Ferris)