Value Collection GH8790511 Counterbore 51/64 in 3 Flute Hss

Product Description

The VALUE COLLECTION GH8790511 is an interchangeable pilot counterbore designed for precision bolt-seat and fastener-recess cutting in metal fabrication and machining applications. The tool features a 51/64-inch counterbore diameter and a 5/8-inch straight shank, with three right-hand flutes ground from high-speed steel for consistent chip evacuation and clean shoulder cuts. The bright, uncoated finish is standard for general-purpose HSS tooling. With an overall length of 5-3/8 inches and a shank length of 3-7/8 inches, this counterbore provides adequate reach for most bench and drill-press setups. Machinists, toolroom technicians, and maintenance mechanics install this type of tooling when a socket-head cap screw or similar fastener requires a recessed seat in steel, aluminum, or cast iron.

This counterbore is suited for use in manual drill presses, milling machines, and CNC machining centers where a straight-shank tool holder or drill chuck accepts a 5/8-inch shank. The interchangeable pilot design allows the operator to swap pilots to match the clearance hole size of the fastener being seated, making the tool adaptable across common bolt patterns. Typical applications include structural fabrication, fixture building, and general machine-shop maintenance work requiring recessed fastener counterbores.

Key Features

• 51/64-inch counterbore diameter for recessing socket-head or similar fasteners
• Interchangeable pilot accepts 1/4-inch pilot shank diameter for flexible hole sizing
• Three right-hand flutes for efficient chip clearance and smooth shoulder finish
• High-speed steel construction provides toughness in ferrous and non-ferrous materials
• Bright uncoated finish suited for general-purpose machining without lubrication buildup
• 5/8-inch straight shank fits standard drill chucks and straight-shank tool holders

Compatibility

Designed as an interchangeable-pilot counterbore compatible with 1/4-inch pilot shanks. Fits machine setups accepting a 5/8-inch straight shank, including drill presses, knee mills, and machining centers.

Installation Notes

Installation is performed by machinists and toolroom technicians. Secure the 5/8-inch straight shank firmly in a drill chuck or straight-shank tool holder before operation, and verify the pilot is fully seated and locked before engaging the workpiece. Ensure the workpiece is clamped securely to prevent movement during the counterboring operation. Use appropriate cutting fluid for ferrous materials to extend tool life and maintain surface finish.