Chicago-Latrobe 69876 29-Piece Left-Hand Helix Jobber Drill Set

29-Piece Left-Hand Helix Jobber Drill Set

This 29-piece drill bit set from Chicago-Latrobe uses high speed steel for general-purpose machining. The left-hand helix design suits specific extraction or reverse-drilling tasks. It is aimed at mechanics and technicians who need a full range of jobber-length bits in one package. Buyers requiring coated bits for extended wear in abrasive materials should look elsewhere.

Left-Hand Helix Geometry

The defining specification is the left-hand helix flute direction combined with a 118-degree point angle. This geometry allows the bit to cut in a counter-clockwise direction, which is essential for removing broken fasteners or operating in reverse-driven setups. Standard right-hand drills cannot perform this function. The bright, uncoated finish is standard for the high speed steel material used.

Thermal Behaviour in Use

High speed steel generates heat during drilling, so cutting fluid or periodic withdrawal is necessary to manage temperature and preserve the 118-degree point. The uncoated bright finish offers no thermal barrier, making lubrication more important than with coated alternatives. Power draw and noise depend entirely on the drill motor and workpiece material rather than the bits themselves.