Kennametal 6140721 Spiral Flute Tap 3/4-10 Cobalt

Product Description

The KENNAMETAL 6140721 is a spiral flute tap designed for cutting 3/4-10 UNC internal threads in ferrous workpiece materials. Built from cobalt high-speed steel with an oxide coating, it handles the heat and abrasion generated when tapping steel, stainless steel, and cast iron. The 45-degree helix angle evacuates chips upward through the flute, keeping the cutting zone clear in through-hole and moderately deep blind-hole applications. Four flutes and a modified bottoming chamfer allow threading close to the bottom of a hole without sacrificing tool stability. Overall length is 4.25 inches. Licensed machinists, tool-and-die makers, and maintenance technicians use this tap in manual or CNC tapping operations.

This tap is suited for production and maintenance applications in steel fabrication, machine shops, and heavy equipment repair. The modified bottoming chamfer provides a short lead-in — typically 1 to 2 threads — making it practical for blind holes where a plug or taper tap would leave unthreaded material too close to the hole bottom. Primary workpiece materials are steel, stainless steel, and cast iron. The H3 thread limit designates a ground thread tolerance appropriate for standard fit classes in UNC 3/4-10 applications.

Key Features

• Cobalt high-speed steel construction resists heat buildup when tapping stainless steel and alloy steels
• 45-degree right-hand spiral flute geometry pulls chips out of the hole during tapping
• Modified bottoming chamfer allows threading close to the bottom of blind holes
• Oxide coating reduces friction and provides baseline lubricity at the cutting edge
• H3 thread limit ground tolerance for consistent fit in standard UNC assemblies
• No coolant-through requirement — compatible with flood or manual lubrication setups

Compatibility

Designed as an OEM-style cutting tool replacement for 3/4-10 UNC tapping applications in steel, stainless steel, and cast iron workpieces. The 0.59-inch shank diameter fits standard tap holders and chucks sized for 3/4-inch taps.

Installation Notes

Installation should be performed by a qualified machinist or maintenance technician familiar with tapping operations. Secure the workpiece fully before engaging the tap, and ensure the tap is aligned perpendicular to the hole to prevent thread distortion or tool breakage. Always apply appropriate cutting fluid or tapping compound for the workpiece material — cobalt taps in stainless steel particularly benefit from sulfurized or chlorinated cutting oils. Inspect the tap for chipping or wear before each use; a damaged cutting edge in a blind hole can result in a broken tap that is difficult to extract.