Precision Twist Drill 5995779 Cobalt Extension Drill 3/16 in

Product Description

The PRECISION TWIST DRILL 5995779 is a cobalt aircraft extension drill bit designed for demanding drilling applications where reach and heat resistance matter. Built to Series CO500-12 standards, this 3/16 inch diameter bit features a 135-degree split point for self-centering starts without a center punch, reducing walking on hard or curved surfaces. The straw finish indicates the cobalt-treated steel has been tempered for added hardness. With a 12 inch overall length, the extended reach suits tight spaces and deep-access drilling common in aerospace, fabrication, and sheet metal work. Licensed tradespeople and skilled machinists are the primary installers.

This drill bit is suited for right-hand cutting in metal, stainless steel, cast iron, and high-hardness alloys where standard HSS bits fall short. The 2-5/16 inch flute length with a 4xD flute-to-diameter ratio provides adequate chip clearance during extended-reach operations. The straight-cylindrical shank fits standard 3-jaw chucks on drill presses, portable drills, and mag-base drills. It is commonly used in aircraft maintenance, structural fabrication, and HVAC sheet metal installations where deep reach into confined areas is required.

Key Features

• 135-degree split point for self-centering starts with no center punch required
• Cobalt construction for improved performance in hardened and abrasive materials
• 12 inch overall length provides extended reach into confined or deep work areas
• Straw finish indicates heat-treated cobalt steel for added wear resistance
• Web-thinned, tapered web configuration reduces thrust and improves chip evacuation
• Straight-cylindrical shank fits standard 3-jaw chucks without an adapter
• Right-hand cutting direction; compatible with conventional drill press and portable drill operation

Compatibility

Designed as a general-purpose cobalt aircraft extension drill bit meeting NAS 907 Type J standards, suitable for use in standard 3-jaw chucks accepting a 3/16 inch straight-cylindrical shank.

Installation Notes

Secure the straight-cylindrical shank firmly in a 3-jaw chuck before operation and verify the bit runs true to minimize runout. Power down and lock out the drill press or de-energize the portable drill before installing or removing the bit. Use appropriate cutting fluid or coolant when drilling hardened alloys to extend bit life and manage heat buildup. Eye protection and appropriate work-holding fixtures should be used at all times per applicable shop safety standards.