Osg 1804100 Hand Sti Tap 4-40 Unc H2 3 Flutes

Product Description

The OSG 1804100 is a hand STI tap designed for cutting STI (Screw Thread Insert) threads in a 4-40 UNC thread form. It features a bottoming chamfer for threading close to the bottom of blind holes, three flutes for chip evacuation, and an H2 thread limit for controlled thread tolerance. Constructed from high speed steel with a bright finish, this tap handles a range of workpiece materials including aluminum, carbon steel, cast iron, and hardened steel. The overall length is 1.875 inches with a thread length of 0.5625 inches. It is a hand tap intended for use with a tap wrench or handle rather than a machine spindle.

This tap is suited for creating threads to accept helical coil inserts in light-gauge fastener applications across maintenance, repair, and manufacturing environments. The 4-40 UNC designation makes it a common choice for small-component work in electronics assembly, instrument repair, and precision mechanical fabrication. The bottoming chamfer style allows threading to within one or two threads of a blind hole floor, making it the correct choice when thread engagement must extend deep into a shallow hole.

Key Features

• Bottoming chamfer allows threading close to the bottom of blind holes
• H2 thread limit provides consistent tolerance for STI thread inserts
• Three-flute design aids chip evacuation during hand tapping
• High speed steel construction suitable for aluminum, carbon steel, cast iron, and hardened steel
• Bright finish - no coating buildup that could affect thread geometry
• Compact overall length of 1.875 inches with 0.5625 inch thread length for small workpiece access

Compatibility

Designed for hand tapping applications requiring 4-40 UNC STI threads to accept screw thread inserts in aluminum, carbon steel, cast iron, and hardened steel workpieces.

Installation Notes

This tap is intended for use by machinists, toolmakers, or maintenance technicians using a manual tap wrench. Always ensure the workpiece is secured and the starting hole is drilled and chamfered to the correct STI tap drill size before threading. Apply appropriate cutting fluid for the workpiece material to reduce tool wear and improve thread finish. Reverse the tap periodically during hand tapping to break chips and prevent tap breakage, especially in blind holes.