Hertel K008981AS Tap Set 5/16-18 Unc 4 Flute Hss

Product Description

The HERTEL K008981AS is a 3-piece tap set designed for cutting 5/16-18 UNC internal threads in metal workpieces. Built from high speed steel with a bright finish, this set delivers the hardness and edge retention needed for production threading in steel, cast iron, and similar ferrous materials. The 4-flute design provides balanced cutting action and chip evacuation in through-hole and blind-hole applications. Overall length is 2-23/32 inches. The set covers 2B and 3B classes of fit, making it suitable for both standard and close-tolerance threaded assemblies.

This tap set is used in machine shops, maintenance facilities, and fabrication environments where 5/16-18 UNC threads must be cut by hand or with a tapping machine. The 3-piece set typically includes a taper, plug, and bottoming tap, allowing the technician to start, advance, and finish threads in a single setup. Applications include repair threading, new hole threading in structural components, and production runs on ferrous stock.

Key Features

• 5/16-18 UNC thread form for standard unified coarse-thread applications
• 4-flute geometry for balanced cutting and chip clearance
• High speed steel construction for hardness and wear resistance on ferrous materials
• Bright finish — no coating that can add dimensional variation to thread tolerance
• 2B and 3B class of fit coverage for standard and close-tolerance assemblies
• H5 thread limit for consistent fit across the thread tolerance range

Compatibility

Designed for use in any application requiring 5/16-18 UNC internal threads cut in ferrous or compatible materials using a standard tap wrench or tapping machine.

Installation Notes

Secure the workpiece fully before threading to prevent movement during the cut. Apply appropriate cutting fluid for the workpiece material to extend tap life and improve thread finish. Back the tap off periodically to break and clear chips, particularly in blind holes. Inspect threads with a go/no-go gauge after cutting to verify class of fit compliance.