The 23-year-old turned heads in the first round when he ousted Robbie Temple, an Englishman ranked 60 places above Butt. The Lahore native went on to take Grayson 4-11, 11-6, 11-8, 11-2.
Butt progresses to face Adrian Grant, the top seed from England. The London left-hander had earlier dismissed Butt's 17-year-old compatriot Danish Atlas Khan in the other quater-final 12-10, 11-9, 11-5. This means that the two Pakistanis will not be facing off against each other in the semi-final.
There will also be English interest in the other semi-final where Chris Simpson takes on Alister Walker, of Botswana.
Fourth seed Simpson staged an impressive comeback, recovering from 2/0 down to beat fellow countryman Adrian Waller 5-11, 2-11, 11-6, 11-7, 11-9 in 71 minutes.
Walker, the second seed, survived a marathon first game before going on to beat English qualifier Olivier Pett 18-16, 11-6, 11-7 in 63 minutes.
Quarter-finals:
[1] Adrian Grant (ENG) bt [Q] Danish Atlas Khan (PAK) 12-10, 11-9, 11-5 (46m)
[Q] Yasir Butt (PAK) bt Campbell Grayson (NZL) 4-11, 11-6, 11-8, 11-2 (56m)
[4] Chris Simpson (ENG) bt Adrian Waller (ENG) 5-11, 2-11, 11-6, 11-7, 11-9 (71m)
[2] Alister Walker (BOT) bt [Q] Olivier Pett (ENG) 18-16, 11-6, 11-7 (63m)
Semi-final line-up:
[1] Adrian Grant (ENG) v [Q] Yasir Butt (PAK)
[2] Alister Walker (BOT) v [4] Chris Simpson (ENG)
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