Power Tool Accessories.
Wood Drill Bits
The Auger bit was originally designed for drilling with a hand brace, however they can be used very effectively in modern power drills. The C.K Auger bit produces a very clean accurate hole and is frequently used where the hole made needs to be splinter free or will be visible.
In the centre of the bit is a tapered screw thread. This screws into the wood as the drill is turned, and pulls the bit into the wood. There is no need for any force to push the bit into the workpiece, only the torque to turn the bit.
So, for each turn of the bit, the cutting edge cuts a slice of wood of thickness equal to the pitch of the central screw. The C.K auger bits have a screw pitch of 2mm therefore it would take around 10 turns to cut through a 20mm piece of wood.
The edge of the bit has a sharpened spur to cut the fibres of the wood, (as for the brad point drill) and a radial cutting edge that planes the wood from the base of the hole.
Auger bits do not cut well in the end grain of wood. The central screw tends to pull out, or to split the wood along the grain, and the radial edges have trouble cutting through the long wood fibres.