Hertel 4139820 Cobalt Jobber Drill 31/64 in Tialn

Product Description

The HERTEL 4139820 is a cobalt jobber-length drill bit designed for heavy-duty holemaking in ferrous and hard-to-machine materials. Built from cobalt high-speed steel and finished with a TiAlN (titanium aluminum nitride) coating, this bit handles elevated cutting temperatures better than standard HSS tooling. The 135-degree split point reduces walking and axial thrust at entry, so pilot holes are rarely needed. With a 31/64-inch diameter and an overall length of 5-7/8 inches, it fits standard drill chucks and drill presses used in fabrication, mechanical, and general industrial applications. The web-thinned, tapered web geometry keeps the cutting edge efficient through the full flute length of 4-3/8 inches.

This bit is suited for machinists, tool-and-die techs, pipefitters, millwrights, and maintenance mechanics who need a reliable jobber drill for production or field work. The straight-cylindrical shank seats securely in keyless or keyed chucks without slipping under load. Right-hand spiral flutes evacuate chips efficiently in through-hole and blind-hole drilling. The heavy-duty grade rating makes it a practical choice for drilling structural steel, stainless, cast iron, and other hard materials where standard HSS bits wear prematurely.

Key Features

• Cobalt construction for superior heat resistance in hard and abrasive materials
• TiAlN coating extends tool life by reducing friction and oxidation at the cutting edge
• 135-degree split point minimizes walking and reduces required thrust force
• Web-thinned, tapered web improves cutting efficiency and chip clearance
• Right-hand regular spiral flutes provide reliable chip evacuation
• Straight-cylindrical shank compatible with standard drill chucks

Compatibility

Designed as a jobber-series replacement or direct-use drill bit for applications requiring a 31/64-inch diameter hole, compatible with standard keyless and keyed drill chucks accepting straight-cylindrical shanks in the 0.4000 to 0.5000 inch decimal range.

Installation Notes

Secure the shank fully in the chuck before operation and verify the chuck is tightened evenly. Power down and lock out the drill press or power tool before changing bits. Use appropriate cutting fluid or coolant when drilling ferrous metals to maximize bit life, even though this bit does not support coolant-through delivery. Follow applicable shop safety standards and wear eye protection during all drilling operations.