Hertel C.E07.0357 Aircraft Drill Bit No. 28 Cobalt

Product Description

The HERTEL C.E07.0357 is a cobalt aircraft extension drill bit designed for deep-reach drilling in aerospace, structural, and industrial applications. Built to NAS 907 standards, it features a 135-degree split point that is self-centering and reduces walking on entry, minimizing the need for a center punch. The two-flute spiral design with a web-thinned, tapered web configuration reduces cutting resistance and chip load. At 12 inches overall length, this bit reaches fastener holes and structural panels that standard-length bits cannot access. The straw finish is typical of cobalt tooling processed for heat resistance and surface hardness.

This bit is sized to wire gauge No. 28, equivalent to 0.1405 inches decimal diameter, and is suited for drilling aluminum, stainless steel, high-strength alloys, and composite materials commonly encountered in aircraft maintenance, sheet metal work, and structural fabrication. The straight cylindrical shank at 0.1405 inches diameter fits standard drill chucks without an adapter. It is appropriate for use with pneumatic or electric right-hand drill motors in both production and MRO environments.

Key Features

• NAS 907 standard cobalt construction for high-heat and abrasion-resistant drilling
• 135-degree split point with web thinning for self-centering entry and reduced thrust
• 12-inch overall length provides extended reach into deep cavities and structural panels
• 1.75-inch spiral flute length for efficient chip evacuation in short-flute cuts
• Right-hand cutting direction with two flutes and tapered web configuration
• Straw finish consistent with cobalt tooling thermal processing

Compatibility

Designed as a general-purpose aircraft extension drill bit for use in right-hand drill motors accepting a straight cylindrical shank of 0.1405 inches diameter. Sized to wire gauge No. 28 per NAS 907.

Installation Notes

This bit is installed and removed by a licensed machinist, aircraft maintenance technician, or qualified sheet metal worker using a standard keyed or keyless chuck. Secure the shank fully in the chuck before applying power to prevent runout or bit ejection. Ensure the workpiece is properly clamped before drilling, especially with extended-length bits where lateral flex can affect hole location. Follow applicable workplace safety and aviation maintenance manual procedures when drilling structural components.