Precision Twist Drill 5995813 Cobalt Drill Bit Letter E

Product Description

The PRECISION TWIST DRILL 5995813 is a cobalt aircraft extension drill bit sized at Letter E (0.2500 inches, or 1/4 inch) with a 135-degree split point and straw finish. Designed for demanding drilling applications in hard and abrasive materials, this bit features a spiral flute, web-thinned tapered web, and a self-centering split point that reduces walking on entry. The 6-inch overall length provides the extended reach typical of aircraft-series bits, making it a practical choice for tight or deep-access drilling situations. Licensed tradespeople and production machinists working with stainless, high-alloy steels, or hard exotics will recognize the cobalt construction as the correct material for sustained heat resistance.

This bit is suited for use in aerospace, HVAC fabrication, structural steel, and general metalworking applications where standard-length bits cannot reach or where heat buildup degrades high-speed steel tooling. The Series CO500-6 designation identifies it as a 6-inch aircraft extension style. With a 2.75-inch flute length and a 4xD flute-to-diameter ratio, it provides sufficient chip clearance for moderate-depth holes in a variety of metals. The straight cylindrical shank fits standard drill chucks without adapters.

Key Features

• Cobalt tool material with straw finish for heat resistance and extended tool life in hard metals
• 135-degree split point with web thinning for self-centering entry and reduced thrust
• 6-inch overall length for extended reach in aircraft-style drilling applications
• 2.75-inch spiral flute length with tapered web configuration for efficient chip evacuation
• Right-hand cutting direction with 1/4-inch straight cylindrical shank for universal chuck compatibility
• Meets NAS 907 Type J standard

Compatibility

Designed as a general-purpose aircraft extension drill bit in Series CO500-6, compatible with any standard drill chuck accepting a 1/4-inch straight cylindrical shank.

Installation Notes

This drill bit is installed by machinists, tool-and-die professionals, HVAC sheet metal workers, and structural fabricators using standard or extended-reach drill presses, hand drills, or magnetic-base drills. Secure the straight shank fully in the chuck jaws before operation and verify runout is within acceptable limits to prevent premature wear. Cobalt bits generate significant heat in hard materials — use appropriate cutting fluid or coolant to extend tool life and avoid work hardening the base material. Follow shop safety procedures including eye protection and proper workpiece clamping.