Duncalf beat fellow Englishwoman Alison Waters 11-4, 11-4, 11-7 in just under 30 minutes.
"I'm pleased with that," said the 27-year-old world No 2 from Harrogate, now in her 16th Tour final - five of which have been against Nicol David.
"We usually have very tough matches, and I was a bit concerned after having such a tough match yesterday, but she didn't play as well as she would have liked.
"I managed to stretch out leads in the first two, and pulled a few back in the third, but she can play better than that.
"I'm really happy to be in the final here for the first time."
It will be Duncalf and David's fourth meeting in a Tour final this year.
David - No 1 since march 2006, defeated Australia's Rachael Grinham 11-9, 11-9, 11-5 in 35 minutes.