Centre Bit
From DT Online
Centre Bits were designed principally for use with a Carpenter's Brace and usually have a Square Tapered Shank for this purpose.
They have a central guide point (originally filed to a triangle), a spur to sever the wood fibres around the circumference, and a single, chisel-edge cutting blade to remove the waste.
Note: Most wood bits will cause splitting if an attempt is made to drill straight through the material. Best practice is to drill from one side until the tip emerges on the reverse then turn the wood around and complete drilling from the other side.