Britain's Anthony Fowler and Andrew Selby secured at least a bronze medal at the World Amateur Championships in Almaty, Kazakhstan.
Unseeded middleweight Fowler beat German Stefan Hartel two rounds to one in the quarter-finals.
Flyweight Selby, the top seed, edged past Kazakhstan's Ilyas Suleimenov 2-1.
However, fellow Welshman and number one seed Fred Evans missed out on a medal as he lost 3-0 to Germany's Arajik Marutjan in the welterweight class.
"It means the world to me and I've trained so hard," 22-year-old Fowler, who lost to seventh seed Hartel at this year's European Championships, told BBC Sport.
"I never stop until the final bell. My diet has been spot on, I'm training hard and I'm getting the rewards."
Fowler faces Kazakhstan's Zhanibek Alimkhanuly in Friday's semi-final while Selby, 25, takes on Jasurbek Latipov after the Uzbekistan fighter beat Northern Ireland's Paddy Barnes 3-0.
The winners of the semi-finals will be guaranteed at least a silver medal.
Northern Ireland's Michael Conlan, the number two seed, lost all three rounds of his last-eight bantamweight fight with Russia's Vladimir Nikitin, who was ranked eight places below him.
Compatriot Tommy McCarthy was beaten by Argentina's number two-ranked Yamil Peralta in their heavyweight quarter-final.
"It was a close fight, but I cannot change it so [there is] no point crying about it," said McCarthy. "There are no positives to be taken in losing."