Cleveland C91698 Solid Pilot Counterbore 0.286in 3 Flute Hss

Product Description

The CLEVELAND C91698 is a solid pilot counterbore designed for creating precision recesses for socket-head cap screws in ferrous and alloy materials. Machined from high-speed steel (HSS) with a bright, uncoated finish, it features a 0.286-inch cutting diameter, a 0.178-inch standard pilot diameter, and three flutes for efficient chip evacuation. The straight-cylindrical shank measures 1/4 inch (0.25 inches) in diameter. At 3 inches overall length, the C91698 is sized for general-purpose counterboring on drill presses, milling machines, and CNC machining centers. Installation is performed by machinists and tool-and-die professionals working in production or maintenance environments.

The C91698 is suited for counterboring operations in alloy tool steel, carbon steel, and cast iron workpieces. Its forward cutting direction and three-flute geometry make it appropriate for through-hole and blind-hole applications where a clean, flat-bottomed recess is required to seat a number-8 socket-head cap screw flush or below the surface. It performs reliably in both manual and CNC-controlled operations where consistent bore diameter and pilot alignment are critical.

Key Features

• 0.286-inch counterbore diameter sized for number-8 socket-head cap screw compatibility
• 0.178-inch standard pilot diameter for accurate bore alignment
• Three-flute geometry promotes chip clearance and smooth cutting action
• High-speed steel construction handles alloy tool steel, carbon steel, and cast iron
• Bright, uncoated finish for direct use without additional surface treatment
• Straight-cylindrical 1/4-inch shank fits standard drill chucks and collets

Compatibility

Designed for use with number-8 socket-head cap screws. Compatible material applications include alloy tool steel, carbon steel, and cast iron. Fits tool holders and chucks accepting a 1/4-inch straight-cylindrical shank.

Installation Notes

Counterbores of this type are installed and operated by machinists using drill presses, milling machines, or CNC equipment. Secure the workpiece firmly before beginning the operation, and ensure the pilot diameter matches the existing pilot hole to prevent tool deflection. Run at speeds appropriate for high-speed steel tooling in the workpiece material, and apply cutting fluid as needed to extend tool life. Inspect the pilot and cutting edges for wear before each use.