Precision Twist R56CO 51/64 Black & Bronze Cobalt Reduced Shank Drill Bits 118 Degree Split Point – 1/2 Shank 092351

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.