Delgado, from Maidenhead, beat the eighth seed, Steven Downs, 6-3,
7-6 to make amends for losing to the New Zealander in the semi-finals of the Australian Junior Open in January. Martin beat his fellow Briton, James Baily, the winner of the Australian tournament, 6-1, 4-6, 7-5.
The slightly built Delgado, 16, trailed 1-3 but then reeled off five successive games for the first set in 33 minutes. He missed two match points at 5-4 in the second set and another two in the tie-breaker which he won 10-8 on his fifth match point.
Martin, 17, from Bristol, did well to come back from a break point down against Baily, the Southampton 17- year-old who was seeded 15th.
Jeremy Bates and the Zimbabwean Bryon Black were beaten 6-4, 6-3, 6-4 by the No 1 seeds, Todd Woodbridge and Mark Woodforde, of Australia, in the men's doubles quarter-finals. Bates and his partner had earlier won the last two sets to beat the German Michael Stich and Wayne Ferreira, of South Africa, 7-6, 4-6, 4-6, 7-5, 6-1. Britain's Paul Hand and Chris Wilkinson also went out, losing 6-4, 6-7, 4-6, 6-3, 6-4 to the Swede Rikard Bergh and South Africa's Byron Talbot.