Osg 6004500 Hand Sti Tap 4-40 Unc H1 3 Flutes Plug Chamfer

Product Description

The OSG 6004500 is a hand STI tap designed for cutting 4-40 UNC threads in a variety of common metals. STI taps produce oversized threads to accommodate Heli-Coil and similar wire thread inserts, making them the correct tool when repairing stripped threads or installing inserts for higher-strength fastener engagement. This tap runs an H1 thread limit for close tolerance work and features 3 flutes with a plug chamfer, which provides a moderate lead-in suited to through-hole and moderately deep blind-hole applications. The tool is ground from High Speed Steel with a bright finish and measures 1.875 inches overall with a 0.5625-inch thread length. Licensed machinists, maintenance techs, and tool-and-die professionals are the primary users.

The OSG 6004500 is suited for hand-tapping operations in repair and production environments where 4-40 UNC threads need to accept wire thread inserts. The H1 tolerance class makes it appropriate for precision fits in light assemblies. Compatible materials include aluminum, carbon steel, cast iron, and hardened steel, covering the broad range of substrates encountered in general maintenance, aerospace component repair, and light manufacturing. Plug chamfer geometry handles most standard through-hole and shallow blind-hole scenarios without requiring a bottoming tap.

Key Features

• STI geometry cuts oversized 4-40 UNC threads to accept Heli-Coil and equivalent wire thread inserts
• H1 thread limit for close-tolerance, precision thread form
• 3-flute plug chamfer design provides controlled lead-in for through-holes and shallow blind holes
• High Speed Steel construction handles aluminum, carbon steel, cast iron, and hardened steel
• Bright finish - no coating interference with close-tolerance fits
• Compact 1.875-inch OAL with 0.141-inch shank suits standard tap wrenches and T-handle drivers

Compatibility

Designed for use with Heli-Coil and equivalent wire thread insert systems requiring 4-40 UNC STI thread form. Confirmed compatible materials include aluminum, carbon steel, cast iron, and hardened steel per OSG Series 126 specifications.

Installation Notes

This tap is intended for hand operation using a properly sized tap wrench - do not run it in a power driver without appropriate torque control. Ensure the workpiece is secured and the tap is started perpendicular to the bore to maintain thread alignment. Apply cutting fluid appropriate for the workpiece material to extend tool life and improve thread quality. Follow Heli-Coil or insert manufacturer specifications for correct drill size prior to tapping.