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Precision Twist R56CO Cobalt Steel Reduced Shank Drill Bit, Black and Gold Oxide Finish, 1/2" Reduced Shank, 118 Degree Split Point

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Product Specifications
Cutting Direction
Finish Types
Gold Oxide
Shank Type
Material Type
Cobalt Steel
Drill Point
Cutting Angle
118  Degrees
Brand Name
Precision Twist
Flute Type

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Key Features

  • High-speed steel (HSS) containing cobalt is a good combination of toughness and hardness, for use on drilling through hard substances
  • Combination black oxide and gold finish, improves lubricity, resists corrosion, and will not chip or flake off
  • Half-inch round shank allows larger sized drills to fit into small size chucks
  • Jobber-length drill bits, most common length drill bit, suitable for a wide range of applications
  • 118-degree split-point angles, for general drilling applications

Product Description

The Precision Twist R56CO Jobber-length, combination black (also called steam tempered) and gold oxide, general-purpose, round shank drill bit drills holes into a wide variety of metals and synthetic materials with best performance with steel, stainless steel, cast iron, titanium, nickel, and copper. It can drill to a depth up to four times the diameter of the drill size. Flute length is three inches, overall length is six inches, with a half-inch, reduced shank.

The R56CO series has a type N flute form (a regular helix angle of 21 to 34 degrees). The combination black oxide and gold finish improves lubricity, resists corrosion, and will not chip or flake off. Black and gold oxide is an appealing surface treatment which combines the benefits of both black oxide and gold oxide. Black oxide finish gives a strongly adhering blue oxide surface that acts to retain cutting fluid and prevent chip to tool welding, reducing the formation of a built-up edge. Gold oxide is a low temperature heat treatment which reduces grinding stress within the tool, and has an appealing, easy-to-identify gold color. Gold oxide is commonly used to identify cobalt steel tools.

Reduced shanks are smaller than the drill diameter, so they can drill holes larger than the typical chuck capacity. These are sometimes called Silver & Deming drills; they used to be made by Silver & Deming in the late 1800s, but now it refers to any reduced shank twist drill bit.

Made of HSS with cobalt which is many times harder/stiffer than HSS, will hold an edge longer, and will deflect less than HSS. These are also more resistant to heat than HSS. These qualities allow it to run at higher speeds and feeds. They are made to ANSI (fractional sizing) industry standards, which ensure that drill bits around the world, conform to the same specifications.

Drilling, or hole making, is the most common metalworking operation in the world. Twist drill bits are the most common type of drill bit used. Twist drill bits are commonly used to drill holes with hand-operated drills, standalone drill presses, or lathes. The flutes of the drill bit act a passageway for chip extraction from the hole and for coolant to enter the hole. These drill bits have a right-hand twist that brings chips up and away from the cutting edge.

Precision manufactures machine tools under the following brands: Precision Twist, Precision Dormer, and Union Butterfield. They have locations around the world, and provide tools adhering to ANSI, NAS, and DIN standards.

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