Osg 7017100 Spiral Point Sti Tap 3/8-16 Unc Hss

Product Description

The OSG 7017100 is a spiral point STI tap designed for threading STI (Screw Thread Insert) holes in a variety of workpiece materials. It features a plug chamfer style and three flutes, with a spiral point geometry that pushes chips ahead of the tap and into the hole for cleaner threading in through-hole applications. Built from high-speed steel with a bright uncoated finish, this tap delivers consistent thread quality on the 3/8-16 UNC standard. The H3 thread limit ensures proper fit for insert installation. Overall length is 2.9375 inches, with a thread length of 0.94 inches and a shank diameter of 0.367 inches.

This tap is intended for use when installing helical thread inserts, such as Heli-Coil style inserts, in a 3/8-16 UNC application. The STI designation means the tap cuts an oversized thread that accommodates the installed insert, resulting in a finished internal thread at the nominal 3/8-16 UNC dimension. Common installation scenarios include repair of stripped threads and original equipment manufacturing where insert-reinforced threads are required. Machinists, maintenance technicians, and production workers in metalworking and repair environments are the primary users. The plug chamfer style suits most through-hole and moderately deep blind-hole work where a gradual thread lead-in is acceptable.

Key Features

• Spiral point geometry pushes chips forward, suited for through-hole tapping
• Plug chamfer provides gradual engagement suitable for most production and repair applications
• H3 thread limit ground for accurate fit with standard STI helical inserts
• High-speed steel construction provides wear resistance across a broad range of workpiece materials
• Bright uncoated finish maintains dimensional precision without coating buildup
• 3 flutes provide a balance of chip clearance and tool strength at this thread size

Compatibility

Designed as an STI tap for use with 3/8-16 UNC helical thread insert systems following the H3 thread limit standard. Confirm insert manufacturer tap size recommendations before use to ensure proper thread fitment.

Installation Notes

This tap is installed by machinists or maintenance technicians using a standard tap wrench, tapping head, or CNC machine spindle with appropriate feed control. Ensure the workpiece is securely fixtured and the pilot hole is drilled to the correct STI tap drill diameter specified by the insert system manufacturer before tapping. Apply cutting fluid appropriate to the workpiece material to extend tap life and improve thread finish. Do not reverse the tap under power without confirming the machine setup supports it, as HSS taps can fracture under side loading or misalignment.