Power Tool Accessories: Drill Bits
Module four: Specialist Electrician's Tools
Wood Drill Bits
Spade bits are used for rough hole cutting in wood and are typically used where the holes cannot subsequently be seen, for instance through floor joists.
Splintered holes can be a problem – they could snag cables being pulled through for instance.
To help reduce splintering (in much the same way as with brad point bits) the C.K flat bit blade is provided with two spurs to cut through the wood fibres before the main blade planes through the bottom of the hole.
They also have a brad point for accurately locating the centre of the hole.
Since flat bits have small shank diameters relative to their boring diameters, the shanks have hexagonal flats to prevent them slipping in the drill chuck.