Hertel G271172-1 Extension Tap 5/16-18 Unc 4 Flute H3

Product Description

The HERTEL G271172-1 is a spiral point plug extension tap designed for cutting internal threads in through-hole applications. Built from high speed steel with a bright, uncoated finish, this tap produces 5/16-18 UNC threads to a 3B class of fit, making it suitable for general-purpose fastener thread forming where standard tap lengths cannot reach. The H3 thread limit provides controlled oversize tolerance to account for material spring-back and tap wear. At 6 inches overall length, the extended reach makes it practical for deep-set bosses, fixtures, and workpieces where a standard-length tap cannot engage the spindle. Licensed machinists, tool and die makers, and maintenance technicians typically use this tap in production and repair environments.

This tap is suited for through-hole threading operations in ferrous and non-ferrous materials where UNC thread forms are specified. The spiral point geometry pushes chips ahead of the cutting action rather than packing them into the flute, which reduces the risk of chip clogging in blind-adjacent through-hole setups. The 4-flute design and plug chamfer provide a balanced cutting action for use in manual and CNC tapping applications requiring extended-reach tooling.

Key Features

• Spiral point plug geometry pushes chips forward, reducing clogging in through-hole applications
• H3 thread limit provides controlled oversize tolerance for consistent 3B class of fit results
• 6-inch overall length gives extended reach for deep workpieces and fixtures
• 4-flute configuration delivers balanced cutting forces for manual and machine tapping
• High speed steel construction offers durability across a range of ferrous and non-ferrous materials
• Bright, uncoated finish — suitable for use with cutting fluids in standard tapping operations

Compatibility

Designed for through-hole tapping operations requiring 5/16-18 UNC threads at a 3B class of fit with extended reach. Fits standard tap holders and chucks accepting the shank diameter of this tool family.

Installation Notes

Always secure the workpiece firmly before tapping and use a suitable cutting fluid for the material being threaded. Power down and lock out any machine before changing or inspecting taps. Verify tap holder alignment to avoid thread angle errors or tap breakage. Follow applicable shop safety and machine guarding standards when operating drilling or tapping equipment.