Flexcoat Pilot Drill Bit
The pilot drill bit guides itself through a pre-existing hole in order to increase the diameter. These tools are made from spade bits with an aluminum pilot on the tip. When used with a hand drill the result is a perfectly centered hole.
Flex Coat Pilot Drill Bits are available in 5/16", 3/8", 7/16", 1/2", 9/16", 5/8".