Indexable Drill Bit

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Indexable drill bits are primarily used in CNC and other high precision or production equipment, and are the most expensive type of drill bit, costing the most per diameter and length. Like indexable lathe tools and milling cutters, they use replaceable carbide or ceramic inserts as a cutting face to alleviate the need for a tool grinder. One insert is responsible for the outer radius of the cut, and another insert is responsible for the inner radius. The tool itself handles the point deformity, as it is a low-wear task. The bit is hardened and coated against wear far more than the average drill bit, as the shank is non-consumable. Almost all indexable drill bits have multiple coolant channels for prolonged tool life under heavy usage. They are also readily available in odd configurations, such as straight flute, fast spiral, multiflute, and a variety of cutting face geometries.

Typically indexable drill bits are used in holes that are no deeper than about 5 times the bit diameter. They are capable of quite high axial loads and cut very fast.

Left-hand bit

An 1/8 inch left-hand drill bit
Left-hand ...
... bits are almost always twist bits and are predominantly used in the repetition engineering industry on screw machines or drilling heads. Left-handed drill bits allow a machining operation to continue where either the spindle cannot be reversed or the design of the machine makes it more efficient to run left-handed. With the increased use of the more versatile CNC machines, their use is less common than when specialized machines were required for machining tasks.

Screw extractors are essentially left-hand bits of specialized shape, used to remove common right-hand screws whose heads are broken or too damaged to allow a screwdriver tip to engage, making use of a screwdriver impossible. The extractor is pressed against the damaged head and rotated counter-clockwise and will tend to jam in the damaged head and then turn the screw counter-clockwise, unscrewing it. For screws that break off deeper in the hole, an extractor set will often include left handed drill bits of the appropriate diameters so that grab holes can be drilled into the screws in a left handed direction, preventing further tightening of the broken piece.

Metal spade bit
A spade drill bit for metal is a two part bit with a tool holder and an insertable tip, called an insert. The inserts come in various sizes that range from 7/16 to 2.5 inches (11 to 64 mm). The tool holder usually has a coolant passage running through it.[9] They are capable of cutting to a depth of about 10 times the bit diameter. This type of drill bit can also be used to make stepped holes.