Hello Ron,
I don't use the brass candle cups. I use a 7/8" spade bit which has about
1/16" remove from each side at the tip of the cutting end. It is tapered so that the bottom of the hole is 3/4" and the top where you insert the candle is 7/8". Don't forget to angle the leading edge of the tapered side. The tapered hole should give you a good fit with most candles.
I've used the same spade bit for over 10 years with only a touch up now and then with a diamond hone card.