Hertel 42155 Cobalt Jobber Drill Bit 21/64 in 135 Deg

Product Description

The HERTEL 42155 is a cobalt jobber length drill bit designed for demanding metal drilling applications. Built from M35 cobalt steel, it delivers heat resistance and edge retention when cutting through stainless steel, cast iron, hardened alloys, and other tough materials. The bit features a 135-degree split point that self-centers on contact, reducing walking and the need for a center punch. With an overall length of 4.625 inches and a flute length of 3.313 inches, it fits standard drill chucks used in both handheld and machine setups. Machinists, pipefitters, and general maintenance technicians install this bit in fabrication, MRO, and field service work.

This drill bit is suited for production and maintenance drilling in metal fabrication shops, mechanical rooms, and job sites. The 21/64 inch diameter (0.3281 inches decimal) makes it a common choice for clearance holes, tapping prep, and through-hole work in both light structural and sheet metal stock. The bright uncoated finish is compatible with cutting fluid application for extended tool life in continuous drilling operations. The straight cylindrical shank seats securely in keyed or keyless chucks across standard drill presses and portable electric drills.

Key Features

• M35 cobalt steel construction for heat and wear resistance in hard-metal drilling
• 135-degree split point self-centers and reduces thrust required to start the cut
• Right-hand cutting spiral flute with regular helix for efficient chip evacuation
• Bright uncoated finish compatible with cutting oils and water-soluble coolants
• Two-flute design with 5xD flute-to-diameter ratio for jobber length reach
• Straight cylindrical shank fits standard drill press and handheld drill chucks

Compatibility

Designed as a jobber length drill bit with a straight cylindrical shank, suitable for use in standard keyed and keyless drill chucks on bench-top drill presses, CNC machines, and portable electric drills accepting bits in the 0.3000 to 0.3500 inch shank diameter range.

Installation Notes

A licensed machinist or qualified maintenance technician should secure the bit firmly in the chuck before operation, verifying there is no runout before engaging the workpiece. Apply cutting fluid or a water-soluble coolant to extend bit life and manage heat when drilling ferrous metals. Reduce feed pressure as the point breaks through the far side of the material to prevent grab or bit breakage. Follow applicable shop safety standards and machine guarding requirements during all drilling operations.