Osg 8011800 Spiral Flute Sti Tap 1/4-28 Unf Bottoming Hss

Product Description

The OSG 8011800 is a spiral flute STI (Screw Thread Insert) tap designed for cutting precise internal threads in a range of ferrous and non-ferrous materials. Built from high-speed steel (HSS) with a bright finish, this tap features a 50-degree helix angle that promotes efficient chip evacuation in through-hole and blind-hole applications. The bottoming chamfer allows threading close to the bottom of a blind hole with minimal runout. The 1/4-28 UNF thread form and H2 thread limit make it a reliable choice for precision thread repair and insert installation in production and maintenance environments.

This tap is suited for use in machine shop, maintenance and repair, and light manufacturing settings where UNF threads are required. The STI designation means it cuts an oversize thread profile intended to accept a helical coil insert such as a Heli-Coil, restoring stripped or damaged threads to original specifications. Compatible with manual tapping handles and machine tap holders in CNC, drill press, and tapping machine setups. Applicable materials include aluminum, carbon steel, cast iron, and hardened steel, making it versatile across a range of workpiece types encountered in industrial and trade maintenance work.

Key Features

• STI thread form cuts oversize profile for helical coil thread insert installation in 1/4-28 UNF applications
• 50-degree helix angle promotes upward chip evacuation, reducing clogging in blind holes
• Bottoming chamfer enables threading to within 1-2 threads of hole bottom
• H2 thread limit provides tight dimensional control for consistent insert fit
• High-speed steel construction offers good wear resistance across aluminum, carbon steel, cast iron, and hardened steel
• Right-hand flute, right-hand cut configuration for standard tapping operations

Compatibility

Designed for use in 1/4-28 UNF STI thread insert applications across aluminum, carbon steel, cast iron, and hardened steel workpieces. Suitable for use with standard helical coil insert systems requiring a 1/4-28 UNF host thread. Part of the OSG Series S108 spiral flute STI tap line.

Installation Notes

Installation should be performed by a qualified machinist or maintenance technician familiar with tapping operations and thread insert systems. Always secure the workpiece and ensure the tap is properly aligned with the pilot hole before beginning the tapping cycle. Apply appropriate cutting fluid for the workpiece material to extend tool life and improve thread quality. When using in a machine setup, verify spindle speed and feed rate are appropriate for the material and tap diameter before engaging the cut.