One is candle size. I need to drill hard curly-maple for the base of the
candles. Nelson sez to use candles with .5" base: I can't find any locally.
But I've got some with 17/32" base.

I've seen devices that will taper down a candle to fit in a holder.
Also you could get a 9/16" spade bit and grind or file the sides down
to a slight taper (or even to cut a cylinder)for holes for the candle.