Osg 10801200 Spiral Flute Sti Tap 5/8-11 Unc Hss

Product Description

The OSG 10801200 is a spiral flute STI (Screw Thread Insert) tap designed for cutting internal threads that accept HeliCoil-style inserts in 5/8-11 UNC applications. Built from high-speed steel with a bright finish, it features 4 right-hand flutes with a 50-degree helix angle that efficiently evacuates chips upward out of the hole during tapping. The bottoming chamfer allows threading close to the bottom of blind holes. With a 3B class of fit and H3 thread limit, this tap produces threads sized appropriately for STI insert installation. It belongs to OSG Series S108 and is intended for use by machinists, maintenance technicians, and tool-and-die professionals.

This tap is suited for production and maintenance environments where damaged or worn threads are being repaired using threaded inserts. The 50-degree helix angle makes it particularly effective in softer materials such as aluminum, cast iron, and mild steel where chip flow out of a blind hole is a priority. The bottoming chamfer design is chosen when thread engagement must extend to the lowest possible point in a blind bore. Overall length of 4.25 inches and a thread length of 2 inches provide adequate reach for typical STI repair operations in both manual and low-speed machine tapping setups.

Key Features

• STI (Screw Thread Insert) tap profile sized for HeliCoil-compatible insert installation in 5/8-11 UNC threads
• 50-degree right-hand spiral flute helix for upward chip evacuation in blind holes
• Bottoming chamfer for threading close to the bottom of blind bores
• High-speed steel construction provides durability across a range of workpiece materials
• H3 thread limit and 3B class of fit for consistent STI thread sizing
• Bright finish with no coating for straightforward regrinding and tool maintenance

Compatibility

Designed as an STI tap for use in 5/8-11 UNC thread repair applications requiring HeliCoil-style threaded inserts. Belongs to OSG Series S108.

Installation Notes

STI taps are installed by qualified machinists or maintenance technicians using a tapping handle, tapping head, or low-speed machine spindle with appropriate cutting fluid. Power down all equipment and secure the workpiece before beginning any tapping operation. Follow the insert manufacturer drill size chart to select the correct STI tap drill before using this tap. Never force a tap against resistance — back off periodically to break chips and re-apply cutting fluid.