Hertel 66691338 Screw Machine Drill Bit Letter E Cobalt

Product Description

The HERTEL 66691338 is a screw machine length drill bit designed for high-production drilling in metal fabrication, machining, and maintenance applications. Built from cobalt steel with a titanium nitride (TiN) coating, the bit delivers extended tool life and heat resistance in tough materials including stainless steel, cast iron, and high-strength alloys. The 135-degree split point reduces thrust and walking on entry, eliminating the need for a center punch on most surfaces. At 2.5 inches overall length, the screw machine format provides added rigidity compared to jobber-length bits, making it well suited for drill press and CNC applications where runout and deflection are concerns.

This bit is sized at Letter E, equivalent to 0.2500 inch decimal, and fits standard straight-cylindrical shank chucks. It is commonly used in production drilling on drill presses, turret lathes, machining centers, and hand-held pneumatic drills where short, stiff tooling reduces breakage. The heavy-duty grade designation and web-thinned, parallel web configuration make it appropriate for repetitive through-hole and blind-hole operations in metal shop and industrial maintenance environments. Machinists, tool and die workers, and industrial maintenance technicians are the primary installers and users.

Key Features

• Cobalt steel construction with TiN coating for heat and wear resistance in ferrous and hard alloys
• 135-degree split point reduces entry thrust and minimizes drill walking without a center punch
• Screw machine length (2.5 inches OAL) provides greater rigidity than jobber-length bits for precision drilling
• Web-thinned parallel web reduces cutting resistance and improves chip evacuation
• Right-hand spiral flute geometry for standard clockwise rotation in conventional drilling setups
• Straight-cylindrical shank fits standard three-jaw chucks and collet systems

Compatibility

Designed for use in any drill press, CNC machining center, turret lathe, or hand-held drill accepting a 0.2500-inch straight-cylindrical shank. Suitable for drilling steel, stainless steel, cast iron, and similar hard materials requiring heavy-duty cobalt tooling.

Installation Notes

Secure the shank fully in the chuck and verify concentricity before drilling to minimize runout. Always power down and lock out the machine before changing tooling per applicable OSHA lockout/tagout procedures. Use appropriate cutting fluid or coolant for the workpiece material to extend tool life, even though this bit does not support coolant-through delivery. Inspect the cutting edges and TiN coating before each use and discard bits showing chipping or coating failure to avoid workpiece damage.