I have many a childhood memory of "helping" to make a chanukiyah out of a block of wood and eight hex nuts glued down to it (often with 2 more stacked in the center for shamash); each hex nut was supposed to hold a candle, but with the standard size chanukah candles, you always had to force the candle or whittle away some of the wax and often the candle got broken in the process.
Is there a readily-available size of standard hex nut that will accommodate a standard sized chanukah candle? (And if so, why didn't any of my Judaica arts-and-crafts teachers think of that?) Is there a size that would fit a big white shabbos candle?