Hertel 66691528 Screw Machine Drill Bit Letter B Cobalt

Product Description

The HERTEL 66691528 is a screw machine length drill bit designed for high-production drilling in tough materials. Built from cobalt high-speed steel with a titanium nitride (TiN) coating, this bit delivers extended tool life and heat resistance in demanding shop and field applications. It measures 2.5 inches in overall length with a 1.375-inch flute length and a 0.2380-inch diameter, corresponding to Letter B sizing. The 135-degree split point reduces walking on contact and requires less thrust to start a hole, making it well-suited for harder workpiece materials. Web-thinned construction further lowers cutting resistance. It is sold and packaged as a single bit.

This drill bit is intended for metalworking applications where a short, rigid drill is preferred over jobber-length tooling. Screw machine length bits are commonly used in CNC lathes, turret lathes, drill presses, and automatic screw machines where tool overhang must be minimized to maintain precision and reduce deflection. The cobalt substrate and TiN coating make it appropriate for drilling stainless steel, alloy steel, cast iron, and other abrasion-resistant metals. The right-hand spiral flute and straight cylindrical shank allow direct mounting in standard drill chucks and collets without additional toolholding adapters.

Key Features

• Cobalt steel construction with TiN coating for extended wear life in hard and abrasive materials
• 135-degree split point reduces thrust requirements and minimizes bit walking at entry
• Web-thinned, parallel-web design lowers cutting resistance throughout the flute
• Screw machine length geometry increases rigidity and reduces deflection in close-tolerance drilling
• Right-hand spiral flute for standard chip evacuation in conventional drilling operations
• Straight cylindrical shank at 0.2380 inches fits standard drill chucks and collets directly

Compatibility

Designed as an OEM-style replacement or standard tooling selection for use in drill presses, CNC lathes, turret lathes, and automatic screw machines accepting a straight cylindrical shank at 0.2380 inches diameter.

Installation Notes

Installation is performed by machinists and toolroom technicians. De-energize and lock out all power to the machine before changing tooling, in accordance with OSHA lockout/tagout procedures. Ensure the shank is fully seated and the chuck or collet is tightened to the machine specification before operation. Do not use this bit without coolant or cutting fluid when drilling hard alloys, as dry cutting will reduce coating life and may cause premature edge failure.