Precision Twist Drill 5995771 Cobalt Aircraft Extension Drill

Product Description

The PRECISION TWIST DRILL 5995771 is a cobalt aircraft extension drill bit engineered for demanding drilling applications in hard and abrasive materials. Built to Series CO500-12 standards, it features a 135-degree split point for self-centering entry without a center punch and a straw finish that indicates the cobalt content used throughout the tool. The straight-cylindrical shank measures 13/64 inch (0.2031 inch decimal) and seats securely in standard drill chucks. With a 12-inch overall length and right-hand spiral flutes, this bit reaches deep into confined areas where standard-length drills cannot. Licensed tradespeople and aerospace maintenance technicians are the primary users.

This drill bit is suited for aircraft maintenance, structural fabrication, and industrial metalworking where extended reach is required. The 2-7/16-inch (2.4375-inch decimal) flute length handles chip evacuation in steel, stainless, titanium, and other hard alloys. The 4xD flute-to-diameter ratio supports controlled feed rates and chip clearance in deep-hole drilling scenarios. Installations in tight airframe bays, structural steel panels, and mechanical assemblies benefit from the 12-inch extension. General-purpose performance rating makes it appropriate for job-site and shop use by machinists, ironworkers, and aviation mechanics.

Key Features

• 135-degree split point provides self-centering entry and reduces walking on hard surfaces
• Cobalt construction resists heat buildup in tough alloys including stainless steel and titanium
• 12-inch overall length gives extended reach into deep or confined work areas
• Straw finish indicates cobalt content and provides mild corrosion resistance
• Web-thinned tapered web reduces thrust and improves cutting efficiency
• Right-hand spiral flutes with 4xD ratio promote consistent chip evacuation

Compatibility

Designed as an OEM-style replacement or direct-use cobalt extension drill in applications requiring a 13/64-inch diameter, straight-cylindrical shank bit conforming to NAS 907 Type J standards.

Installation Notes

Secure the shank fully in the chuck before drilling and confirm the workpiece is clamped or fixtured to prevent movement. Use cutting fluid appropriate to the workpiece material to extend tool life and reduce heat in cobalt drills. Wear ANSI-rated eye protection and ensure drill speed matches the manufacturer or machinist handbook recommendation for the material and diameter. Inspect the bit for chipping or wear at the split point before each use.