Hertel K007322AS 1/4-28 Unf Spiral Flute Sti Tap Hss

Product Description

The HERTEL K007322AS is a spiral flute STI tap designed for cutting Screw Thread Insert (STI) threads in a variety of metals and harder materials. Built from high-speed steel with a bright finish, it cuts a 1/4-28 UNF thread profile using three flutes and a 52-degree helix angle. The bottoming chamfer allows threading close to the bottom of a blind hole, making it well suited for tight-tolerance repair and fabrication work. With an overall length of 2-23/32 inches, it fits standard tap wrenches and machine tool holders. This tap is used by machinists, maintenance technicians, and toolroom professionals wherever STI thread repair or insert preparation is required.

The K007322AS is intended for applications where a HeliCoil-type insert will be installed after tapping, restoring or upgrading thread strength in parent material. It is appropriate for use in ferrous and non-ferrous metals in both manual hand-tapping setups and low-speed machine tapping operations. The bottoming chamfer design is particularly useful in blind-hole applications where full thread depth close to the hole bottom is required. Helicoil reference number 5906-4 identifies the compatible insert series for this thread size and pitch.

Key Features

• 1/4-28 UNF thread size and pitch for fine-thread STI insert preparation
• 52-degree helix angle promotes efficient chip evacuation in blind holes
• Bottoming chamfer allows threading to within 1-2 threads of the hole bottom
• Three-flute geometry balances cutting load and chip clearance
• High-speed steel construction provides durability across a range of workpiece materials
• Bright finish with H2 thread limit for consistent dimensional accuracy

Compatibility

Compatible with HeliCoil reference number 5906-4 inserts. Designed as an STI tap for use in thread repair and insert installation applications requiring a 1/4-28 UNF thread form.

Installation Notes

Installation is performed by qualified machinists or maintenance technicians using a standard tap wrench or tapping head. Before tapping, ensure the workpiece is securely clamped and the pilot hole is drilled to the correct STI tap drill size for the 1/4-28 UNF thread. Apply cutting fluid appropriate for the workpiece material to reduce heat and improve thread quality. Back the tap off periodically to break chips and prevent tap breakage, particularly in deeper blind holes.