Precision Twist Drill 5995759 Cobalt Extension Drill Bit Letter E

Product Description

The PRECISION TWIST DRILL 5995759 is a cobalt aircraft extension drill bit sized at Letter E (0.2500 inches / 1/4 inches) with a 135-degree split point and a 12-inch overall length. The extended reach and cobalt construction make it suited for drilling through hard metals, stainless steel, and high-strength alloys where standard-length bits cannot reach. The split point is self-centering, eliminating the need for a center punch on most surfaces. A straw finish indicates the heat treatment applied during manufacturing. This bit is installed by machinists, aircraft maintenance technicians, pipefitters, and industrial tradespeople working in tight or deep-access drilling applications.

The 5995759 is designed for general-purpose drilling in aircraft, structural, and heavy industrial applications where extended reach is required. The 12-inch overall length with a 2.75-inch flute length gives the bit the clearance needed to drill through thick or layered materials while maintaining chip evacuation through the spiral flute design. The straight cylindrical shank accepts standard drill chucks without an adapter. Right-hand cutting direction is standard for conventional drill press and handheld drill use.

Key Features

• Letter E (1/4 inches / 0.2500 inches) cobalt construction for drilling hard metals and alloys
• 135-degree split point with self-centering geometry reduces walking without center punch
• 12-inch overall length for extended reach in deep or obstructed drilling scenarios
• Spiral flute with 2.75-inch flute length (4xD ratio) promotes chip evacuation
• Straight cylindrical shank fits standard drill chucks directly
• Web-thinned tapered web reduces thrust and cutting resistance
• Meets NAS 907 Type J standard for aircraft-grade drill bits

Compatibility

Designed as an OEM-style replacement or direct-fit drill bit for standard 1/4-inch straight-shank drill chucks used in aircraft maintenance, industrial fabrication, and general metalworking applications.

Installation Notes

A licensed machinist or qualified technician should verify chuck compatibility and secure the shank fully before operation. Ensure the workpiece is clamped or fixtured before drilling to prevent movement. Use appropriate cutting fluid when drilling hard alloys to extend tool life and reduce heat buildup. Follow applicable shop safety standards and PPE requirements when operating rotary cutting tools.