Most common drill bits are of the twist bit variety and are so called because the flutes on the bit twist around and up the bit. Typical twist drill bits have flutes that twist to the right in a clockwise direction. Less commonly seen are left-handed drill bits, which have flutes that twist in a left-handed or counter-clockwise direction.
Left-handed drill bits were once used when it was easier to change the drill bit than it was to change the rotation of the drill.
Left-handed drill bits are available in many different sizes and lengths, but their limited use can make them difficult to find.
General-use twist bits are the most common form of left-handed drill bit, but some have flatted shanks to prevent twisting in the drill chuck.
Removal of broken fasteners is the most common use for left-handed drill bits. Since right-handed fasteners are loosened by turning to the left, the torque applied by a lefthanded drill bit loosens the fastener.
Fasteners that have broken off in a threaded hole can be a time-consuming problem to repair. Left-handed drill bits can save time and money by easing removal of the broken fastener.
