Value Collection 191-4K Reverse Counterbore Solid Carbide

Product Description

The VALUE COLLECTION 191-4K is a solid carbide reverse counterbore designed for spot facing operations on the reverse or blind side of a workpiece. With a 7/16-inch counterbore diameter, a 5/32-inch pilot hole diameter, and four flutes, this tool delivers clean, flat bearing surfaces in applications where standard counterbores cannot reach. The 1/2-inch overall length makes it compact and suitable for confined-space holemaking. Machinists and tool and die professionals working in aerospace, automotive, or general manufacturing will find this tool well suited to precision back-spotfacing tasks.

This reverse counterbore is used in metalworking and machining environments where a fastener seat or flat bearing surface must be created on an inaccessible face. It is typically installed in a CNC machining center or manual milling setup. The tool accepts a standard pilot or an oversize pilot, allowing the operator to select the fit that matches the drilled hole condition. Applications include back-spotfacing for bolt clearance, flush-mounting hardware, and similar precision holemaking operations in both production and maintenance settings.

Key Features

• Solid carbide construction for hardness, wear resistance, and dimensional stability in demanding cuts
• 7/16-inch counterbore diameter with a 5/32-inch pilot hole for precise centering
• Four-flute geometry for improved chip evacuation and surface finish
• 1/64-inch corner radius reduces stress concentration at the seat transition
• Compatible with standard pilot model 185-3 and oversize pilot model 186-3
• Compact 1/2-inch overall length suited for tight-clearance reverse spotfacing

Compatibility

Accepts standard pilot model number 185-3 and oversize pilot model number 186-3. Designed as an OEM-style replacement or direct-use reverse counterbore for holemaking setups requiring back-spotfacing with a 5/32-inch pilot and 7/16-inch seat diameter.

Installation Notes

Installation and operation should be performed by a qualified machinist familiar with reverse counterboring procedures. Power down and lock out the machine spindle before changing or securing the pilot in the tool body. Use appropriate cutting fluid for the workpiece material to extend tool life and maintain surface finish. Follow shop safety protocols and applicable machining standards when operating carbide cutting tools at speed.