Precision Twist Drill 5999025 Letter I Cobalt Jobber Drill

Product Description

The PRECISION TWIST DRILL 5999025 is a Letter I cobalt jobber-length drill bit designed for general-purpose drilling in steel and other demanding workpiece materials. It features a 135-degree split point with web thinning for reduced walking and easier starts without a center punch. The 0.272-inch diameter straight shank and regular spiral flute geometry deliver consistent chip evacuation during through-hole and moderate-depth drilling operations. At 4.125 inches overall length with a 2.875-inch flute length, this bit fits standard three-jaw chucks on drill presses, hand drills, and CNC drilling setups. A straw oxide finish provides light lubricity and corrosion resistance during storage and use. This bit is intended for installation by machinists, maintenance technicians, and industrial trade professionals.

The 5999025 is suited for drilling ferrous metals, stainless steel alloys, cast iron, aluminum, and non-ferrous materials where cobalt-grade performance is required. Its NAS 907 specification rating makes it appropriate for aerospace, heavy fabrication, and general metalworking applications. The right-hand cutting direction is compatible with standard clockwise-rotation drill presses and portable power tools. It performs best in materials classified under workpiece material codes P, M, K, N, and S, covering a broad range of steels and alloys encountered in trade and industrial shop environments.

Key Features

• Cobalt high-speed steel construction for heat resistance when drilling hardened and alloy steels
• 135-degree split point with web thinning reduces thrust force and eliminates center-punch dependency
• Straw oxide finish provides light lubricity and corrosion protection
• Regular spiral flute with tapered web configuration promotes efficient chip clearing
• Straight cylindrical shank at 0.272 inches diameter fits standard drill chucks without adapters
• NAS 907 specification compliance for aerospace and heavy-duty industrial use

Compatibility

Part of the PRECISION TWIST DRILL Series R10CO-R15CO-R18CO. Designed as a general-purpose cobalt jobber drill bit for use in standard three-jaw drill chucks accepting straight cylindrical shanks up to 0.272 inches in diameter.

Installation Notes

Installation and use of this drill bit should be performed by qualified machinists or trained trade professionals. Secure the shank fully in the chuck and confirm concentricity before drilling. Apply appropriate cutting fluid when drilling hardened steel or stainless alloys to extend tool life and manage heat buildup. Never exceed the drill press or power tool manufacturer's recommended speed and feed for the workpiece material and bit diameter.