Value Collection GH8790255 Counterbore 25/64in 3 Flute Hss

Product Description

The VALUE COLLECTION GH8790255 is a 3-flute interchangeable pilot counterbore designed for precision enlarging and finishing of bolt-hole seats in metal workpieces. It features a 25/64-inch counterbore diameter and a 3/8-inch straight shank, giving it solid tool-holder compatibility across standard drill presses and milling machines. The cutting geometry is right-hand direction with a bright, uncoated high speed steel construction that handles general-purpose ferrous and non-ferrous materials. With a 4-1/16-inch overall length and a 3-1/16-inch shank length, the tool provides adequate reach for most typical countersinking and spotfacing applications encountered by machinists and tool-and-die professionals.

This counterbore is suited for machine shops, maintenance facilities, and production environments where consistent bolt-seat geometry is required. The interchangeable pilot design accepts a 5/32-inch pilot shank, allowing the operator to swap pilots for different fastener clearance holes without changing the body. It performs well on standard drilling equipment and manual or CNC mill setups. Typical applications include preparing seats for socket head cap screws and similar fasteners in steel, aluminum, and cast iron workpieces.

Key Features

• 25/64-inch counterbore diameter for precise bolt-seat sizing
• Interchangeable pilot design accepts 5/32-inch pilot shank diameter
• 3-flute right-hand cutting geometry for smooth material removal
• High speed steel construction for durability across ferrous and non-ferrous materials
• Bright, uncoated finish — no additional coating buildup affecting tolerances
• Straight 3/8-inch shank fits standard drill chucks and collet holders

Compatibility

Designed as an OEM-style interchangeable pilot counterbore compatible with standard straight-shank tool holders accepting a 3/8-inch shank; accepts 5/32-inch interchangeable pilots.

Installation Notes

This tool is installed and operated by machinists using standard drill presses, knee mills, or CNC machining centers. Secure the straight shank firmly in a drill chuck or collet before operation, and verify pilot fit before engaging the workpiece. Always power down and lock out the machine before changing pilots or inspecting the cutting edges. Do not exceed the recommended spindle speed range for high speed steel tooling in the material being machined.