Cleveland C91699 Solid Pilot Counterbore 0.316in 3 Flute Hss

Product Description

The CLEVELAND C91699 is a solid pilot counterbore designed to create clean, accurately sized recesses for socket-head cap screws in ferrous and alloy materials. Machined from high-speed steel (HSS) with a bright, uncoated finish, this tool delivers consistent cutting performance in alloy tool steel, carbon steel, and cast iron. It features a 0.316-inch counterbore diameter, a 0.187-inch standard pilot diameter, and three flutes for efficient chip evacuation. The straight-cylindrical shank measures 5/16 inch in diameter, and the overall length is 3.5 inches. This counterbore is a production-grade tool suited for machine shops, toolrooms, and maintenance departments handling threaded-fastener work.

The C91699 is sized specifically for No. 10 socket-head cap screw compatibility, making it a direct-fit solution for jobs requiring a properly proportioned counterbore seat. Its forward cutting direction and three-flute geometry support use in drill press, milling machine, and manual lathe setups. Typical applications include creating fastener recesses in structural steel components, tooling plates, and fabricated assemblies where cap screw heads must sit flush or below the workpiece surface.

Key Features

• 0.316-inch counterbore diameter sized for No. 10 socket-head cap screws
• 0.187-inch standard pilot diameter for accurate recess alignment
• Three-flute design promotes efficient chip removal during cutting
• High-speed steel construction handles alloy tool steel, carbon steel, and cast iron
• Straight-cylindrical 5/16-inch shank fits standard drill chucks and collets
• Bright, uncoated finish — no additional surface treatment to affect dimensional tolerance

Compatibility

Designed for use with No. 10 socket-head cap screws. Suitable for workpiece materials including alloy tool steel, carbon steel, and cast iron.

Installation Notes

This tool is installed and operated by machinists and maintenance technicians. Secure the straight-cylindrical shank in an appropriate drill chuck or collet rated for the spindle speed being used. Set spindle speed according to the workpiece material and counterbore diameter before starting the cut. Inspect the pilot for wear before each use, as a worn pilot will produce an off-center recess.