Osg 1299200 Spiral Flute Extension Tap 5/8-11 Unc H3 Hss

Product Description

The OSG 1299200 is a spiral flute extension tap designed for cutting 5/8-11 UNC internal threads in applications where standard-length taps cannot reach. Built from high-speed steel with a bright uncoated finish, this plug-chamfer tap operates with a 50-degree helix angle and four flutes, which helps evacuate chips efficiently in through-hole applications. The reduced shank design and 6-inch overall length provide the reach needed for recessed bosses, deep counterbores, and extended-depth features. Licensed machinists, toolroom technicians, and CNC operators typically use this tap in production and maintenance threading operations.

This extension tap is suited for threading aluminum, carbon steel, and cast iron workpieces. The H3 thread limit and 3B class of fit make it appropriate for standard commercial tolerance threading where moderate fit clearance is acceptable. The plug chamfer - typically 3 to 5 thread leads - allows it to start in a through hole and progress smoothly through the full thread depth. With a neck length of approximately 2.129 inches and a shank diameter of 0.48 inches, the tool is compatible with standard tap holders and extension tap adapters used in both manual and machine tapping setups.

Key Features

• Spiral flute design at 50-degree helix angle promotes upward chip evacuation in through-hole threading
• High-speed steel construction provides good wear resistance across a range of ferrous and non-ferrous materials
• Plug chamfer entry for clean thread starts in through-hole applications
• Reduced shank allows reach into recessed or deep-pocket features
• H3 thread limit with 3B class of fit for standard commercial thread tolerances
• Bright uncoated finish suitable for use with cutting fluids on aluminum, carbon steel, and cast iron

Compatibility

Designed for use in aluminum, carbon steel, and cast iron workpieces requiring 5/8-11 UNC threads to a 3B class of fit. Compatible with standard tap holders and extension tap adapters sized for a 0.48-inch shank diameter.

Installation Notes

This tap should be installed in a properly sized tap holder or floating tap adapter to prevent breakage from misalignment. Always use an appropriate cutting fluid matched to the workpiece material before beginning the tapping cycle. Ensure the spindle speed and feed rate are set per the tool manufacturer recommendations for the material being tapped. Follow OSHA machine guarding and lockout/tagout procedures before changing or setting tooling in any machine tool.