Taper a bit to snugly fit plugs and candles
It's hard to get wood plugs to fit snugly into the holes you drill for them. Also, when boring holes for tapered candles, a standard spade bit will not produce a snug fit. The holes will be either too large at the bottom or too small for the base to be inserted properly.
Grind a slight taper on the cutting edges of some spade bits. With these tapered bits, plugs will fit into their holes like a cork into a bottle. Just a few strokes of the file or a pass or two over the grinder will suffice. Make sure both sides have identical tapers. For candles, modify a spade bit of the appropriate size—15⁄16 " matches standard tapered candles. Scribe lines on the bit so it tapers from a 15⁄16 " diameter to 3⁄4 " as shown above.
—John Wolf, St. Joseph, Mich.