Osg 1813600 Hand Sti Tap 1/2-13 Unc H3 4 Flute

Product Description

The OSG 1813600 is a hand STI tap designed for cutting screw-thread inserts in a 1/2-13 UNC thread form with an H3 thread limit. It features 4 flutes and a plug chamfer, making it well suited for starting in through-holes or deeper blind holes where full chamfer engagement is needed before cutting begins. Manufactured from high-speed steel with a bright, uncoated finish, this tap holds up to general-purpose threading operations across a range of common materials. The overall length is 3.375 inches with a thread length of 1.656 inches, giving the tool proper reach for standard insert-depth applications. Licensed machinists, maintenance technicians, and tool-room operators are the typical users.

This tap is used when installing helical thread inserts, commonly known as STI (Screw Thread Insert) inserts, into tapped holes that need to accept a standard 1/2-13 UNC fastener. Suitable for both shop and field use, it performs in materials including aluminum, carbon steel, cast iron, and hardened steel. The plug chamfer style makes it a practical choice for production and repair threading where the tap is started by hand or with a tap wrench in a pre-drilled hole of the correct STI tap drill size.

Key Features

• 1/2-13 UNC thread form with H3 thread limit for controlled fit and insert compatibility
• Plug chamfer allows progressive thread engagement, suitable for through-holes and deeper blind holes
• 4-flute design provides chip clearance and stable cutting action across common workpiece materials
• High-speed steel construction supports use in aluminum, carbon steel, cast iron, and hardened steel
• Bright, uncoated finish - inspect cutting edges easily and resharpen as needed
• OSG Series 126 - a recognized STI tap series for insert preparation work

Compatibility

Designed for use with 1/2-13 UNC helical thread inserts (STI type) in standard STI tap drill size pre-drilled holes. Compatible with aluminum, carbon steel, cast iron, and hardened steel workpieces as stated by the manufacturer.

Installation Notes

Use the correct STI tap drill size for a 1/2-13 UNC insert before tapping - using a standard tap drill will produce an undersized hole. Apply cutting fluid appropriate for the workpiece material; dry tapping hardened steel is not recommended. Secure the workpiece before tapping and use a calibrated tap wrench or tapping fixture to maintain perpendicular alignment with the hole axis. Follow shop safety practices for cutting tool handling, including eye protection and proper tool storage.