Osg 8013700 Spiral Flute Sti Tap 5/16-24 Unf Hss

Product Description

The OSG 8013700 is a spiral flute STI (Screw Thread Insert) tap designed for cutting internal threads that accept helical inserts, also known as wire thread inserts. Built from high-speed steel with a bright finish, this tap produces a 5/16-24 UNF thread form with a right-hand flute orientation. The 50-degree helix angle efficiently evacuates chips during the tapping operation, making it well-suited for blind-hole applications where chip packing is a concern. The bottoming chamfer allows threading close to the bottom of a hole. Overall length is 2-23/32 inches with a shank diameter of 0.381 inches and a thread length of 1-1/8 inches. Machinists and maintenance technicians use this tool in manual or CNC tapping operations where insert-thread repair or original installation is required.

This tap is intended for creating STI threads in a range of materials including aluminum, carbon steel, cast iron, and hardened steel. It is appropriate for both production environments and maintenance repair operations (MRO) where stripped or damaged threads need to be restored using helical inserts. The bottoming chamfer style makes it particularly useful when full thread depth is needed near the bottom of a blind hole, a common requirement in close-tolerance assemblies and thread repair work on fastener bosses.

Key Features

• STI thread form for use with helical screw thread inserts in 5/16-24 UNF applications
• 50-degree helix angle promotes upward chip evacuation in blind holes
• Bottoming chamfer allows threading to near full depth in blind-hole bores
• High-speed steel construction with bright finish for general-purpose tapping across multiple materials
• H3 thread limit for controlled fit with standard STI insert tolerances
• Right-hand flute direction compatible with standard tapping chucks and tap handles

Compatibility

Designed for use with 5/16-24 UNF STI helical insert systems. Suitable for aluminum, carbon steel, cast iron, and hardened steel workpieces per OSG Series S108 specifications.

Installation Notes

Installation should be performed by a machinist or qualified technician familiar with tapping operations and thread insert procedures. Ensure the workpiece is securely fixtured and the pilot hole is drilled to the correct STI tap drill size before tapping. Apply appropriate cutting fluid for the workpiece material to extend tool life and improve thread quality. Operate at recommended speeds for high-speed steel tooling in the given material to avoid tap breakage.