Osg 34201301 Spiral Point Sti Tap M20 X 2.5 Metric Coarse

Product Description

The OSG 34201301 is a spiral point STI tap designed to cut M20 x 2.5 metric coarse thread inserts in through-hole applications. STI taps produce an oversized thread that accepts Heli-Coil style threaded inserts, restoring or reinforcing threads in worn, stripped, or high-stress bores. This tap is ground from vanadium high-speed steel and finished with a black oxide coating, offering improved lubrication retention and moderate corrosion resistance. With a 3-flute spiral point geometry, it pushes chips forward ahead of the cutting zone, making it well suited for tapping in materials where chip evacuation must be controlled. Overall length is 4.9375 inches and thread length is 2.1875 inches.

This tap is used in metalworking, maintenance, repair, and overhaul operations where a threaded insert is required to replace damaged threads or to provide a stronger thread in softer base materials. Typical applications include repair of bolt holes in aluminum castings, cast iron housings, steel fabrications, and similar industrial components. The plug chamfer style provides a gradual lead-in, making it appropriate for through-hole tapping in production and repair environments. It belongs to OSG Series 342STI and carries a 6H class of fit with a D5 thread limit, suitable for standard tolerance insert thread applications.

Key Features

• Spiral point geometry pushes chips forward for clean through-hole tapping
• Vanadium high-speed steel construction for wear resistance in ferrous and non-ferrous materials
• Oxide finish improves lubrication retention and reduces galling
• Plug chamfer provides gradual thread engagement suitable for through-hole applications
• 6H class of fit with D5 thread limit for consistent insert thread tolerance
• STI profile produces oversized thread to accept Heli-Coil style threaded inserts

Compatibility

Designed for use with M20 x 2.5 metric coarse STI threaded inserts in through-hole tapping operations. Compatible with standard Heli-Coil style insert systems requiring a 6H class of fit at D5 thread limit. Suitable for use in steel, cast iron, aluminum, and similar machinable materials.

Installation Notes

Installation is performed by machinists or maintenance technicians using a tap wrench, tapping arm, or CNC machining center with appropriate tap holder. The bore must be drilled to the correct STI tap drill diameter before tapping. Apply cutting fluid appropriate to the workpiece material and power down or secure the workpiece before beginning the operation. Follow shop safety procedures and verify thread gauge acceptance after tapping to confirm proper fit for the insert.