Osg 8013000 Spiral Flute Sti Tap 5/16-18 Unc Hss

Product Description

The OSG 8013000 is a high-speed steel spiral flute STI tap designed to cut Screw Thread Insert (STI) threads in a range of workpiece materials. It features a 50-degree helix angle that efficiently evacuates chips upward out of the hole, making it well-suited for bottoming applications where blind holes require thread cut close to the bottom. The bottoming chamfer provides minimal lead-in, allowing the tap to thread as deep as possible. At 2-23/32 inches overall length with a 0.381-inch shank diameter, this tap is sized for standard tapping chucks and CNC or manual drilling equipment. Machinists and maintenance technicians working with STI inserts on production or repair jobs are the primary users.

This tap cuts 5/16-18 UNC threads to an H3 thread limit, which suits close-tolerance tapping in aluminum, carbon steel, cast iron, and hardened steel. It is used in applications where a Heli-Coil or similar threaded insert is being installed to repair stripped threads or to create a stronger threaded boss in softer base materials. The right-hand flute direction is standard for conventional right-hand thread cutting. The bright finish means no coating is applied, keeping the tap at base HSS hardness and making it easy to inspect for wear.

Key Features

• 50-degree helix angle for upward chip evacuation in blind-hole STI tapping
• Bottoming chamfer allows threading close to the bottom of blind holes
• H3 thread limit provides controlled fit for STI insert installation
• High-speed steel construction compatible with aluminum, carbon steel, cast iron, and hardened steel
• Bright finish for easy wear inspection and no coating buildup in tight-tolerance holes
• Right-hand flute, right-hand cut - compatible with standard tapping setups

Compatibility

Designed for cutting 5/16-18 UNC STI threads per Series S108 specifications. Suitable for use with standard Heli-Coil and equivalent 5/16-18 UNC threaded insert installation in aluminum, carbon steel, cast iron, and hardened steel workpieces.

Installation Notes

This tap is installed by machinists or maintenance technicians using a standard tapping chuck, tap wrench, or CNC tapping cycle. The drill press or machine spindle should be stopped and locked out before changing or inspecting the tap. Use appropriate cutting fluid for the workpiece material - particularly important when tapping hardened steel or cast iron. Do not exceed the recommended feed rate for the helix angle, as forcing a spiral flute tap can cause breakage in the flute gullets.