Kennametal 6140638 Spiral Flute Tap 1/4-20 Cobalt

Product Description

The KENNAMETAL 6140638 is a spiral flute tap designed for threading 1/4-20 internal threads in ferrous materials. Built from cobalt high-speed steel with an oxide coating, it handles the heat and tool pressure common in steel, stainless steel, and cast iron applications. The modified bottoming chamfer allows threading closer to the bottom of a blind hole than a standard taper or plug tap. With a 45-degree helix angle and a fast flute style, chips are efficiently evacuated up and out of the hole during the tapping cycle. Overall length is 2.5 inches with a thread length of 0.63 inches. This tap is used by machinists, maintenance technicians, and tool-and-die professionals working in production or MRO environments.

This tap is suited for blind-hole and through-hole threading operations in steel, stainless steel, and cast iron workpieces. The modified bottoming chamfer provides roughly 1 to 2 threads of lead-in, making it a practical choice when full thread depth close to the hole bottom is required. The right-hand flute direction and right-hand thread form match standard 1/4-20 UNC fastener specifications. Tapping depth reaches 1.0 inch, giving adequate thread engagement for most structural and mechanical fastening applications in both production and repair settings.

Key Features

• Cobalt high-speed steel construction for improved heat and wear resistance in tough ferrous materials
• Oxide coating reduces friction and provides light lubricity during the cut
• Modified bottoming chamfer for threading near the bottom of blind holes
• 45-degree helix angle with fast flute style for efficient upward chip evacuation
• H3 thread limit for consistent fit in standard 1/4-20 UNC tolerance applications
• Right-hand thread and right-hand flute direction for conventional tapping setups

Compatibility

Designed for threading 1/4-20 UNC internal threads in steel, stainless steel, and cast iron workpieces. Compatible with standard tap wrenches and machine holders accepting a 0.255-inch shank diameter. No coolant-through capability; use with external cutting fluid appropriate for the workpiece material.

Installation Notes

This tap is installed by machinists and maintenance technicians using a tap wrench, tapping head, or CNC machine tool holder. Ensure the pilot hole is drilled to the correct tap drill size for 1/4-20 threads before starting. Apply appropriate cutting fluid for the workpiece material to reduce friction and extend tap life. Never force a tap that has stalled in a blind hole; back off to clear chips before continuing to avoid breakage.