Cleveland C13143 Aircraft Extension Drill Bit No. 21

Product Description

The CLEVELAND C13143 is a No. 21 wire-size aircraft extension drill bit designed for drilling in hard-to-reach locations where standard-length bits fall short. Built from high-speed steel (HSS) with a bright/uncoated finish, this bit features a 135-degree split point that self-centers on contact, reducing walking and the need for a center punch. The extended 6-inch overall length combined with a 2.125-inch spiral flute makes it well suited for production and maintenance drilling in aerospace, automotive, and general metalworking environments. A right-hand spiral flute and web-thinned tapered web reduce cutting resistance and improve chip evacuation. Diameter is 0.1590 inches with a tight tolerance of +0.0000 to -0.0007 inches, ensuring consistent hole sizing.

This bit is intended for use in applications requiring extended reach through sheet metal, aluminum, steel, and similar materials. Its straight cylindrical shank is compatible with standard drill chucks. Aircraft maintenance technicians, sheet metal workers, and machinists working in confined or deep-clearance drilling situations will find this bit appropriate for the task. It conforms to NAS 907 Type B standards, which is a common requirement in aerospace and defense fabrication environments. The general-purpose tool performance rating makes it a practical choice across a wide range of ferrous and non-ferrous drilling applications.

Key Features

• 135-degree split point self-centers on the workpiece, eliminating drill walk
• Web-thinned tapered web reduces thrust force and improves chip flow
• 6-inch overall length provides extended reach into deep or obstructed work areas
• High-speed steel construction for durability across metalworking applications
• Meets NAS 907 Type B standard for aerospace-grade drill bit requirements
• Tight diameter tolerance of +0.0000 to -0.0007 inches for consistent hole quality

Compatibility

Designed as a general-purpose aircraft extension drill bit for use in standard drill chucks accepting a straight cylindrical shank at 0.1590-inch diameter. Suitable for drilling operations in aerospace, automotive, and industrial sheet metal applications where NAS 907 Type B compliance is required.

Installation Notes

Installation should be performed by qualified machinists or maintenance technicians familiar with drill press, hand drill, or pneumatic drill operation. Secure the straight shank firmly in the drill chuck before operation and verify the chuck key is removed before starting. Use appropriate cutting fluid or lubricant when drilling ferrous metals to extend tool life and maintain hole tolerance. Inspect the bit for wear or chipping before each use, and do not force the bit through the workpiece as this can cause breakage or diameter deviation.