Osg 1806600 Sti Hand Tap 1/4-28 Unf H2 Plug Chamfer

Product Description

The OSG 1806600 is a straight-flute STI (Screw Thread Insert) hand tap ground to a 1/4-28 UNF thread form with an H2 thread limit and plug chamfer. It is manufactured from high speed steel with a bright finish and produces internal threads sized to accept helical thread inserts in aluminum, carbon steel, cast iron, and hardened steel workpieces. The plug chamfer provides a gradual lead-in suited to through-hole and moderately deep blind-hole applications. With a 1.0000-inch thread length and a 2.5-inch overall length, this tap fits standard hand-tap wrenches used in maintenance, repair, and overhaul work across HVAC, plumbing, electrical, and general mechanical trades.

STI taps are used wherever a damaged or stripped thread is being restored using a helical insert system. The 1/4-28 UNF fine-thread form is common on equipment panels, valve bodies, sensor ports, and fastener bosses where vibration resistance and close thread engagement are required. This tap is the threading step in the insert installation process and is used after drilling the correct STI tap drill diameter. It is suited to bench work, field repair, and light production tapping by hand.

Key Features

• 1/4-28 UNF thread form with H2 thread limit for consistent fit with standard helical inserts
• Plug chamfer with 3-5 thread lead-in for versatile use in through holes and most blind holes
• 3 flutes for chip clearance in a range of materials including hardened steel
• High speed steel construction for durability in hand-tapping applications
• Bright finish - no coating to affect thread tolerance
• 0.2550-inch shank diameter fits standard hand-tap wrenches and T-handles

Compatibility

Designed for use in STI thread insert repair systems requiring a 1/4-28 UNF tapped hole. Compatible with aluminum, carbon steel, cast iron, and hardened steel base materials per OSG Series 126 specifications.

Installation Notes

Installation is performed by hand using a tap wrench; secure the workpiece before tapping and align the tap perpendicular to the drilled hole. Drill the correct STI tap drill size prior to use - the STI tap drill diameter is larger than a standard 1/4-28 tap drill. Apply cutting fluid appropriate for the base material to extend tool life and improve thread finish. Back the tap out periodically to clear chips, especially in blind holes or when working cast iron or hardened steel.