Osg 1294501 Extension Tap 10-24 Unc H3 Spiral Point

Product Description

The OSG 1294501 is a spiral point plug extension tap designed for threading operations in extended-reach applications where a standard-length tap cannot access the workpiece. Built from high-speed steel with a steam oxide finish, it cuts right-hand threads to the 10-24 UNC standard with an H3 thread limit for consistent tolerance control. The 4-inch overall length and reduced shank design allow the tap to reach deep into bores or recessed features. The 2-flute spiral point geometry pushes chips forward ahead of the cutting zone, making it well-suited for through-hole threading. This tap is installed by machinists and tool-and-die professionals using a tap wrench, drill press, or CNC tapping cycle.

This extension tap is used in production and maintenance machining environments where threading must be performed in hard-to-reach locations. It is suited for threading cast iron, aluminum castings, aluminum, and carbon steel workpieces. The plug chamfer style requires a pre-drilled or bored through-hole before tapping. The 7/8-inch thread length and 2B class of fit make it appropriate for standard-tolerance fastener applications in both light-duty and structural assemblies.

Key Features

• Spiral point plug geometry drives chips forward for clean through-hole threading
• H3 thread limit provides consistent fit for 2B class-of-fit requirements
• 4-inch overall length with reduced shank for extended-reach access
• High-speed steel construction handles cast iron, aluminum, and carbon steel
• Steam oxide finish reduces friction and provides light corrosion resistance
• Right-hand flute and right-hand thread direction for standard tapping setups

Compatibility

Designed as a direct-use extension tap for through-hole 10-24 UNC threading in cast iron, aluminum casting, aluminum, and carbon steel. Compatible with standard tap wrenches and machine tool holders accepting a 0.194-inch shank diameter with a 0.152-inch square drive.

Installation Notes

This tap is installed by qualified machinists or maintenance technicians. Ensure the workpiece is securely fixtured and the tap is properly aligned to the pre-drilled hole before beginning the threading cycle to avoid tap breakage. Cutting fluid or tapping compound appropriate for the workpiece material should be applied throughout the operation. Do not force or back-drive the tap at excessive torque.