Precision Twist Drill 5999069 Cobalt Jobber Drill Bit Letter T

Product Description

The PRECISION TWIST DRILL 5999069 is a cobalt jobber-length drill bit sized to letter T (0.358 inches decimal) with a 135-degree split point and a straw oxide finish. Designed for general-purpose drilling in steel and other ferrous and non-ferrous metals, it features a right-hand cutting direction, regular spiral flute geometry, and a web-thinned, tapered web for reduced thrust at entry. The straight cylindrical shank seats directly in standard drill chucks without an adapter. This bit is built to heavy-duty grade and conforms to ANSI and NAS 907 standards, making it a reliable choice for production and maintenance drilling environments.

This drill bit is suited for drilling steel (P, M, K, N, S workpiece material codes) in both shop and field applications. The 4.875-inch overall length and 3.5-inch flute length give it reach appropriate for through-holes in structural members, plates, and fabricated assemblies. It is commonly used by machinists, maintenance technicians, pipefitters, and ironworkers who require consistent sizing across letter-series drill sets. The cobalt composition provides elevated heat resistance compared to standard high-speed steel, supporting higher feed rates in harder stock without premature edge breakdown.

Key Features

• Letter T size — 0.358 inches decimal — for precise hole sizing without reaming in many applications
• Cobalt construction with straw oxide finish for improved heat resistance and extended tool life in steel
• 135-degree split point with web thinning reduces walking and lowers required thrust on entry
• Regular spiral flute promotes efficient chip evacuation in through-hole drilling
• Straight cylindrical shank fits standard 3-jaw drill chucks on drill presses and hand drills
• Conforms to ANSI and NAS 907 standards; rated for general-purpose heavy-duty service

Compatibility

Part of the PRECISION TWIST DRILL Series R10CO-R15CO-R18CO cobalt jobber drill line. Designed as a direct-fit replacement or standalone addition to letter-series drill sets used with standard straight-shank drill chucks on bench drill presses, magnetic drills, and hand-held power drills.

Installation Notes

Installation is performed by machinists, fabricators, or maintenance technicians using standard drill press or hand-drill equipment. Secure the straight shank fully in the chuck jaws and tighten with a chuck key before applying power. Ensure the workpiece is clamped or fixtured to prevent rotation during drilling. Use appropriate cutting fluid or coolant on harder steel grades to manage heat and protect the cutting edge, even though coolant-through is not available on this bit.