Hertel 04139259 Cobalt Jobber Drill Bit No 78 135 Deg

Product Description

The HERTEL 04139259 is a No. 78 wire-size cobalt jobber drill bit designed for precision holemaking in hard and abrasive materials. The bit measures 0.0160 inches in diameter with a 7/8-inch overall length and a 3/16-inch flute length. A 135-degree split point allows the bit to self-center on contact, reducing walking and the need for a center punch. The oxide and TiN coating improves surface hardness and wear resistance. Right-hand spiral flutes with a regular helix clear chips efficiently during drilling. This bit is suited for use by machinists, tool-and-die tradespeople, and precision fabricators working in production or maintenance environments.

The 04139259 is intended for small-diameter holemaking applications in ferrous and non-ferrous metals, stainless steel, cast iron, and other hard materials where standard high-speed steel bits wear prematurely. Its heavy-duty cobalt construction makes it a practical choice for repeated use in production drilling setups, maintenance repair operations, and precision metalworking applications. The straight-cylindrical shank fits standard drill chucks across a wide range of bench-top and handheld drilling equipment. It falls within the 0.0000 to 0.0500-inch drill bit size range typical of wire-gauge jobber series tooling.

Key Features

• No. 78 wire size, 0.0160-inch diameter for precision small-hole applications
• Cobalt construction rated heavy duty for use in hard and abrasive materials
• 135-degree split point self-centers on contact and reduces drill walk
• Oxide and TiN dual coating improves wear resistance and tool life
• Right-hand spiral flutes with tapered web configuration for efficient chip evacuation
• Straight-cylindrical shank compatible with standard drill chucks

Compatibility

Designed as an OEM-style jobber series replacement drill bit for standard straight-chuck drilling equipment used in metalworking and precision fabrication applications within the 0.0000 to 0.0500-inch wire-gauge size range.

Installation Notes

Installation and use of small-diameter drill bits should be performed by a qualified machinist or trade professional familiar with cutting speeds and feeds for cobalt tooling. Secure the straight-cylindrical shank firmly in a properly sized drill chuck before operation to prevent runout or bit breakage. At this diameter, excessive lateral force or off-axis pressure will snap the bit; use a drill press or guided fixture where possible. Follow applicable workplace safety standards and wear appropriate eye protection during all drilling operations.