Cleveland C91728 Solid Pilot Counterbore 29/32 in 3 Flute Hss

Product Description

The CLEVELAND C91728 is a solid pilot counterbore designed for precision spotfacing and counterboring operations in ferrous and alloy materials. Built from high-speed steel (HSS) with a bright, uncoated finish, it delivers reliable cutting performance across alloy tool steel, carbon steel, and cast iron. The tool features a 29/32-inch counterbore diameter, a 21/32-inch standard pilot diameter, and three flutes for efficient chip evacuation. With an overall length of 8.25 inches and a 3/4-inch straight-cylindrical shank, it is sized for rigid toolholder setups on mills and drill presses. Machinists, tool-and-die workers, and maintenance technicians are the primary users.

This counterbore is matched to 5/8-inch socket-head cap screws, making it a direct fit for preparing recessed seat holes to the correct diameter and depth for that fastener standard. It is suited for job shop, production, and MRO applications where counterbored holes must seat SHCS fasteners flush or below the workpiece surface. Common applications include fixture plates, machine bases, and structural assemblies machined from carbon steel, alloy tool steel, or cast iron.

Key Features

• 29/32-inch counterbore diameter sized for 5/8-inch socket-head cap screws
• 21/32-inch standard pilot diameter for accurate hole registration
• Three-flute geometry promotes chip clearance and smooth cutting action
• High-speed steel construction handles alloy tool steel, carbon steel, and cast iron
• 3/4-inch straight-cylindrical shank fits standard toolholders and drill chucks
• Bright/uncoated finish — no coating thickness to affect dimensional tolerance

Compatibility

Designed for use with 5/8-inch socket-head cap screws. Compatible with workpiece materials including alloy tool steel, carbon steel, and cast iron. Fits toolholders and drill chucks accepting a 3/4-inch straight-cylindrical shank.

Installation Notes

Counterbores are installed and operated by machinists using milling machines, drill presses, or similar machine tools. Secure the shank fully in the toolholder and verify runout before cutting. Use appropriate cutting fluid for the workpiece material to extend tool life and maintain surface finish. Follow shop-standard speeds and feeds for HSS tooling in the specific material being machined; do not exceed the rated cutting envelope for high-speed steel.