Precision Twist Drill 5999029 Cobalt Jobber Drill Bit Letter J

Product Description

The PRECISION TWIST DRILL 5999029 is a cobalt jobber-length drill bit sized to Letter J (0.2770 inches decimal) with a 135-degree split point and a straw oxide finish. Manufactured from cobalt high-speed steel, it delivers increased heat and wear resistance compared to standard HSS tooling, making it well suited to demanding ferrous and exotic-alloy drilling applications. The web-thinned, tapered-web point geometry reduces thrust load at entry and improves self-centering. Overall length is 4.125 inches with a 2.875-inch flute length and a straight cylindrical shank. This is a heavy-duty, general-purpose jobber drill intended for use by machinists, tool-and-die professionals, and maintenance mechanics working with industrial drilling equipment.

The 5999029 is designed primarily for drilling steel and a broad range of metallic workpiece materials including cast iron, non-ferrous alloys, and certain high-temperature alloys, consistent with ISO material group codes P, M, K, N, and S. The regular spiral flute and 10xD flute-to-diameter ratio make it appropriate for through-hole and blind-hole drilling in production and MRO environments. It is compatible with standard drill presses, milling machines, and hand-held drilling equipment that accept straight-shank bits. The series designation R10CO-R15CO-R18CO identifies the cobalt product family within the Precision Twist Drill line.

Key Features

• Cobalt HSS construction for elevated heat resistance during steel and alloy drilling
• 135-degree split point with web thinning reduces thrust and improves self-centering without a center punch
• Straw oxide finish provides light lubricity and corrosion protection
• Regular spiral, 2-flute design promotes efficient chip evacuation in deep holes up to 2.875 inches
• Straight cylindrical shank fits standard drill chucks without adapters
• Meets ANSI and NAS 907 dimensional standards for consistent interchangeability

Compatibility

Designed as an OEM-style jobber drill for use in standard drill press chucks, CNC machining centers, and hand-held power tools accepting straight-shank bits sized to 0.2770 inches. Suitable for primary workpiece material groups P, M, K, N, and S per the supplier specification. Part of the Precision Twist Drill Series R10CO-R15CO-R18CO cobalt drill family.

Installation Notes

Installation is performed by machinists and maintenance professionals. Secure the shank fully in a properly sized drill chuck and verify chuck key is removed before starting the spindle. For best results, apply cutting fluid or coolant when drilling hard steels or stainless alloys, even though this bit does not have a coolant-through design. Inspect the cutting edges for wear before each use; cobalt bits can be resharpened but require a grinding wheel appropriate for cobalt-grade tooling.