Cleveland C91717 Solid Pilot Counterbore 41/64 in 3 Flute Hss

Product Description

The CLEVELAND C91717 is a solid pilot counterbore designed for precision spotfacing and counterboring operations in ferrous and alloy materials. The tool features a 41/64-inch counterbore diameter, a 29/64-inch standard pilot diameter, and three flutes for balanced chip evacuation and a clean seat finish. The straight-cylindrical shank measures 1/2 inch in diameter, and the overall length is 7 inches. Constructed from high-speed steel with a bright, uncoated finish, the C91717 is sized for 7/16-inch socket-head cap screws. It is installed and used by machinists, tool-and-die workers, and maintenance mechanics performing counterbore operations on production or repair workpieces.

This counterbore is suited for use in ferrous metals including alloy tool steel, carbon steel, and cast iron. It is sized specifically for 7/16-inch socket-head cap screw clearance, making it a practical tool for machine assembly, fixture building, and structural fabrication work where a recessed fastener seat is required. The standard pilot maintains concentricity with an existing through-hole during the operation, reducing runout and improving seat squareness in both vertical and horizontal mill setups.

Key Features

• 41/64-inch counterbore diameter sized for 7/16-inch socket-head cap screws
• 29/64-inch standard pilot diameter for positive hole alignment
• Three-flute geometry supports balanced cutting and effective chip removal
• High-speed steel construction handles alloy tool steel, carbon steel, and cast iron
• Bright uncoated finish — no coating thickness to account for in close-tolerance work
• Straight-cylindrical 1/2-inch shank fits standard drill press and milling machine chucks
• 7-inch overall length provides clearance for deep-pocket or fixture applications

Compatibility

Designed for use with 7/16-inch socket-head cap screws. Suitable for counterboring operations in alloy tool steel, carbon steel, and cast iron workpieces. Compatible with any drill press, knee mill, or machining center equipped with a chuck or collet accepting a 1/2-inch straight shank.

Installation Notes

This tool is installed by machinists and maintenance mechanics using standard drill chucks or end-mill holders accepting a 1/2-inch straight shank. Secure the workpiece firmly before operation and ensure the pilot seats fully in the existing pilot hole before engaging the cutting edges. Use appropriate cutting fluid for the workpiece material to extend tool life and improve seat finish. Follow shop safety standards for rotating cutting tools, including proper RPM selection for the diameter and material being cut.