For drilling long holes for the lamp flex. Capable of drilling through the centre of standard lamp sections up to about 36" long. Because the tip of the auger does not have a point it tends not to follow the grain of the wood.
You drill (through the tailstock and guide bush) part way through the length of the wood. You have to stop somewhere or you will damage the auger by hitting the drive centre if you break through. You then have to reverse the wood to drill the other end to complete the hole. This is where the counterbore/drive comes in. The 5/16" pilot fits into the auger hole and drives the wood, replacing the normal drive centre.