Cleveland C91703 Solid Pilot Counterbore 3/8 in Hss

Product Description

The CLEVELAND C91703 is a solid pilot counterbore designed for precision counterboring of socket-head cap screw seats in metalworking applications. Built from high-speed steel with a bright uncoated finish, this tool features a 3/8 inch counterbore diameter, a 1/4 inch standard pilot diameter, and three flutes for efficient chip evacuation. The straight-cylindrical 3/8 inch shank provides secure clamping in standard drill press or milling machine chucks. With an overall length of 5.75 inches, this counterbore is suited for machinists and tool-and-die professionals who need consistent, accurate seat geometry on ferrous and alloy workpieces.

This counterbore is intended for use on alloy tool steel, carbon steel, and cast iron in machine shop, production, and maintenance environments. It is compatible with 1/4 inch (No. 12) socket-head cap screws, making it a direct-fit tool for creating properly sized recesses that allow fastener heads to sit flush or below the workpiece surface. Typical applications include fixture building, die work, and structural fabrication where fastener head clearance is required.

Key Features

• 3/8 inch counterbore diameter sized for 1/4 inch socket-head cap screws
• Standard 1/4 inch pilot (0.2500 inch) keeps the bore concentric with the pilot hole
• 3-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 — no coating buildup concerns at standard cutting speeds
• 5.75 inch overall length provides reach for deeper workpiece access

Compatibility

Designed for use with 1/4 inch socket-head cap screws (fastener size No. 12) in standard counterboring operations on alloy tool steel, carbon steel, and cast iron workpieces.

Installation Notes

This tool is installed by machinists and tool-and-die technicians in drill press or milling machine setups. Secure the straight-cylindrical shank firmly in a properly sized chuck or collet before operation. Ensure the workpiece is clamped securely and the pilot hole is pre-drilled to match the 1/4 inch pilot diameter before engaging the counterbore. Use appropriate cutting fluid for the workpiece material to extend tool life and maintain surface finish quality.