Hertel 66691726 Screw Machine Drill Bit Letter W Cobalt

Product Description

The HERTEL 66691726 is a screw machine length drill bit designed for high-production drilling in metal fabrication, machining, and maintenance applications. Sized at Letter W (0.3860 inches), this bit is ground from cobalt steel and finished with a titanium nitride (TiN) coating to extend cutting life in abrasive and work-hardening materials. The 135-degree split point geometry reduces walking on entry and lowers thrust requirements, making it well suited for harder metals and interrupted cuts. Overall length is 3.25 inches with a 1.875-inch flute length, keeping the tool rigid in short-reach setups. The straight cylindrical shank fits standard drill chucks without modification.

This bit is intended for use in screw machines, drill presses, and CNC machining centers where a compact, stubby profile improves rigidity and reduces deflection. It is appropriate for drilling carbon steel, alloy steel, stainless steel, and cast iron in both job-shop and production environments. The heavy-duty grade designation and cobalt substrate make it a practical choice when standard high-speed steel bits wear prematurely. Machinists, tool-and-die technicians, and maintenance mechanics are the primary users.

Key Features

• Letter W size - 0.3860 inches decimal equivalent, within the 0.3500 to 0.4000 inch range
• Cobalt steel construction with TiN coating for extended tool life in hard and abrasive materials
• 135-degree split point reduces entry walking and cutting thrust
• Web-thinned parallel web geometry improves chip evacuation and reduces heat buildup
• Screw machine (stub) length profile increases rigidity and minimizes deflection
• Right-hand cut with regular spiral flutes and straight cylindrical shank for standard chuck compatibility

Compatibility

Designed as a direct-fit replacement screw machine length drill bit for any standard drill chuck or collet accepting a 0.3860-inch straight cylindrical shank.

Installation Notes

Secure the shank fully in a properly sized drill chuck or collet before operation. Ensure the machine spindle is fully stopped and locked out before changing bits. Use appropriate cutting fluid or coolant for the workpiece material to maximize tool life, noting that this bit does not support through-coolant delivery. Follow applicable shop safety standards and machine manufacturer guidelines for speed and feed settings.