Cleveland C91729 Solid Pilot Counterbore 31/32 in Hss

Product Description

The CLEVELAND C91729 is a solid pilot counterbore designed for precision spot-facing and counterboring operations in metalworking applications. Built from high-speed steel (HSS) with a bright, uncoated finish, it delivers reliable cutting performance in alloy tool steel, carbon steel, and cast iron. The tool measures 31/32 inches in counterbore diameter with a 21/32-inch pilot diameter, a 3/4-inch straight-cylindrical shank, and an overall length of 8.25 inches. Three flutes provide efficient chip clearance and a clean bore finish. Machinists and tool-and-die professionals specify this counterbore when working with 5/8-inch socket-head cap screws, where accurate seat depth and concentricity are critical.

The C91729 is suited for manual and CNC machining centers, knee mills, and drill presses where counterboring operations are performed on ferrous metals. Its standard pilot configuration ensures the tool self-locates in an existing drilled hole, keeping the counterbore concentric without additional fixturing. Typical applications include fabrication shops, maintenance and repair operations, and production environments working with structural assemblies, machinery frames, and tooling plates that require a recessed socket-head fastener seat.

Key Features

• 31/32-inch counterbore diameter sized for 5/8-inch socket-head cap screw clearance
• 21/32-inch standard pilot diameter for self-locating in pre-drilled holes
• High-speed steel construction for cutting alloy tool steel, carbon steel, and cast iron
• 3/4-inch straight-cylindrical shank for compatibility with standard tool holders and drill chucks
• 3-flute geometry promotes efficient chip evacuation and a smooth counterbore seat
• Bright, uncoated finish — ready to run at standard HSS speeds and feeds

Compatibility

Designed for use with 5/8-inch socket-head cap screws. Cuts alloy tool steel, carbon steel, and cast iron. Straight-cylindrical shank fits standard drill chucks and tool holders accepting a 3/4-inch shank.

Installation Notes

Install and remove this counterbore only with the machine spindle at a complete stop. Secure the 3/4-inch shank firmly in a compatible chuck or tool holder before operation, and verify pilot clearance in the existing drilled hole before engaging the cut. Follow shop safety practices and applicable OSHA machining standards when operating rotating cutting tools. Do not exceed the recommended surface footage for high-speed steel in the material being cut.