Hertel 52440708 Cobalt Drill Bit No. 21 135 Degree Split Point

Product Description

The HERTEL 52440708 is a cobalt threaded-shank drill bit designed for drilling into high-tensile-strength metals where standard HSS bits fail or wear prematurely. It carries a No. 21 wire size designation with a decimal diameter of 0.1590 inches and an overall length of 1.25 inches. The 135-degree split point geometry self-centers on contact, reducing the need for a center punch and minimizing walking on hard or curved surfaces. A web-thinned, tapered-web construction lowers thrust requirements, and the oxide coating improves surface hardness and lubricity. This bit is sized for production and maintenance environments where precise hole diameter and clean entry matter.

This bit is built for use in high-tensile-strength metals including alloy steels, stainless, and similar hard materials encountered in aerospace, industrial fabrication, and mechanical assembly work. The 1/4-28 threaded shank mates with compatible quick-change or threaded-shank drill holders used in production setups. With a flute length of 0.5625 inches (9/16 inches) and a short overall length of 1.25 inches, it is suited to confined spaces and close-tolerance drilling operations where a longer bit would flex or chatter. It conforms to NAS 965 Type D specification, making it appropriate for aerospace and defense maintenance applications.

Key Features

• Cobalt construction with oxide coating for extended tool life in hard metals
• 135-degree split point self-centers and reduces walking on entry
• Web-thinned, tapered web reduces axial thrust during drilling
• 1/4-28 threaded square shank for use with compatible threaded-shank holders
• Short OAL of 1.25 inches improves rigidity in tight clearance applications
• Meets NAS 965 Type D specification

Compatibility

Designed for use with threaded-shank drill holders accepting a 1/4-28 shank thread. Intended for general-purpose drilling in high-tensile-strength metals per NAS 965 Type D specification.

Installation Notes

Install and remove this bit only with the drill press or power tool fully de-energized and the chuck or holder confirmed stationary. Ensure the threaded shank is fully engaged and seated in the holder before operation. Use appropriate cutting fluid or lubricant when drilling hard or stainless alloys to prevent work hardening and premature bit wear. Right-hand cutting direction only - do not run in reverse.