The Precision Twist R18CO jobber-length drill bit is a 135-degree spilt-point, heavy duty, round shank drill bit made of high speed steel (HSS) and cobalt with a gold oxide finish. They meet NAS 907 Type J, aircraft industry specifications for heat resistance and use for drilling hard, tough materials. Best performance with drilling into hardened, tempered alloy steel, nodular graphite malleable cast iron, titanium, and alloyed nickel. It is suitable for drilling to a depth up to four times the diameter of the drill. The shank diameter is the same as the drill size.
While the R18CO series was designed for aircraft industry, they also work well for drilling into a variety of materials. The 135-degree split point drill geometry help ensure an accurate hole by reducing walking when the hole is started. The finish retains lubricants to aid in wear resistance and chip flow.
The R18CO series has a type N flute form (a regular helix of 21 to 34 degrees). The 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.
Made of HSS with cobalt which is many times harder/stiffer than HSS, it will hold an edge longer, and 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.
and away from the cutting edge.