Threaded Drill Bits #21

#21 Threaded Shank Cobalt Drill Bits for Aircraft Maintenance

#21 threaded shank cobalt drill bits are precision drilling tools designed for aircraft maintenance, repair, and overhaul applications. These threaded shank adapter drills are manufactured to NAS 965 Type D standards and feature a 135-degree split point for accurate starting and controlled drilling.

The #21 drill size provides a small-diameter option for precision drilling applications involving aircraft sheet metal, components, and fastener holes. The 1/4-28 threaded shank is designed for use with compatible threaded drill adapters, creating a compact drilling setup that can be advantageous when working in confined aircraft maintenance areas.

Cobalt construction provides increased heat resistance and durability for demanding drilling applications. The combination of cobalt construction, a 135-degree split point, and threaded shank makes these drills a specialized option for technicians who require precision and compact tooling.

#21 Threaded Drill Bit Sizes and Lengths

BAC offers the #21 threaded cobalt drill in four overall lengths. The different configurations allow technicians to select the appropriate amount of reach while keeping the drilling setup as compact as the application permits.

Why Use a #21 Threaded Shank Drill Bit?

Aircraft maintenance frequently requires small, accurately positioned holes in areas where access is limited. The #21 threaded shank drill provides a compact drilling option while retaining the durability and heat resistance of cobalt construction.

• #21 drill size: Provides a small-diameter drill size for precision aircraft drilling and fastener-hole applications.
• 1/4-28 threaded shank: Designed for use with compatible threaded drill adapters and drilling systems.
• Cobalt construction: Provides increased heat resistance and durability for demanding drilling operations.
• 135-degree split point: Helps the drill start accurately and reduces walking when beginning a hole.
• NAS 965 Type D: Manufactured to the requirements associated with NAS 965 Type D threaded shank adapter drills.
• Four length options: Long, short, stub, and very stubby configurations provide flexibility for different aircraft drilling environments.

#21 Drill Bits for Aircraft Maintenance

#21 threaded drills are suited to precision drilling operations involving aircraft sheet metal, structural components, and small fastener holes. The threaded-shank configuration can be especially useful where a conventional drill chuck and drill-bit combination is difficult to position.

The range of available lengths gives aircraft maintenance technicians additional flexibility when working around aircraft structure, components, and other obstructions. The stub and very stubby configurations allow the overall drilling setup to remain compact in restricted work areas.

Choosing the Correct #21 Drill Length

Drill length should be selected based on the accessibility of the drilling location and the amount of reach required. Whenever practical, use a configuration that provides adequate access without unnecessary drill length.

The 3/8" very stubby provides the most compact configuration and is useful when working in extremely restricted spaces. The 9/16" stub provides slightly more reach while remaining compact. The 1-1/4" short version provides a balance between compactness and reach, while the 2-1/8" long version provides the greatest reach.

NAS 965 Type D Threaded Shank Drill

These #21 threaded shank adapter drills are manufactured to NAS 965 Type D standards and feature a 135-degree split point. The NAS 965 Type D designation identifies a specific aerospace tooling configuration for threaded shank adapter drills.

Threaded Shank Drill Bits for Confined Aircraft Areas

A threaded shank drill can provide a more compact drilling arrangement when paired with a compatible adapter. This is valuable when aircraft structure, installed components, or limited workspace restrict the ability to position a conventional drill and chuck.

The #21 size combined with four available lengths gives technicians multiple options for approaching restricted drilling locations. In particular, the stub and very stubby configurations can help minimize the overall length of the drilling setup.

#21 Threaded Drill Bit Specifications