Precision Twist Drill 5997851 Cobalt Jobber Drill No. 9

Product Description

The PRECISION TWIST DRILL 5997851 is a No. 9 wire-size cobalt jobber drill bit designed for production and maintenance drilling in steel and other demanding workpiece materials. The bit measures 0.1960 inches in diameter with an overall length of 3.625 inches and a flute length of 2.4375 inches. The 135-degree split point — produced through web thinning — reduces walking on entry and lowers thrust requirements compared to a standard 118-degree geometry. An oxide and straw coating provides a bronze-tinted surface treatment that aids lubricity and resists heat buildup during cutting operations. The straight cylindrical shank fits standard drill chucks without adapters. This bit is built to NAS 907 and ANSI standards for dimensional consistency.

This jobber drill is suited for through-hole and blind-hole drilling in steel, cast iron, nonferrous alloys, and high-temp alloys across a range of applications — indicated by its P, M, K, N, and S workpiece material codes. Typical install scenarios include fabrication shops, HVAC equipment manufacturing, plumbing rough-in metalwork, electrical panel fabrication, and general mechanical maintenance. The 12xD flute-to-diameter ratio provides adequate chip clearance for standard-depth holes without the need for a longer-series bit. It is sold and shipped as a single drill bit per package.

Key Features

• Cobalt high-speed steel construction for heavy-duty drilling in hardened and abrasive steels
• 135-degree split point with web thinning reduces entry thrust and minimizes bit walking
• Oxide and straw coating improves surface lubricity and heat resistance
• Tapered web configuration maintains core strength through the full flute length
• Straight cylindrical shank with zero flats — compatible with standard drill chucks
• Meets NAS 907 and ANSI dimensional standards for consistent, repeatable performance

Compatibility

Part of the R10CO-R15CO-R18CO series. Designed for use in standard drill chucks accepting a 0.1960-inch straight shank. Suitable for drilling steel, cast iron, nonferrous metals, and high-temperature alloys as defined by workpiece material codes P, M, K, N, and S.

Installation Notes

Installation is performed by machinists, maintenance technicians, and trade professionals using standard drill presses, hand drills, or CNC spindles. Secure the shank fully in the chuck and verify runout before drilling. Use appropriate cutting fluid or coolant when drilling hardened steel to extend tool life — this bit does not support through-coolant delivery. Follow shop safety protocols including eye protection and secure workpiece clamping before operation.