Hertel K008311AS Straight Flute Tap 1/4-20 Unc Hss

Product Description

The HERTEL K008311AS is a straight flute tap designed to cut 1/4-20 UNC internal threads in a range of workpiece materials. Built from high-speed steel with a bright, uncoated finish, this tap features four flutes and a taper chamfer for gradual thread engagement at the start of the cut. The taper chamfer distributes cutting forces across several leading threads, making it well-suited for through-hole applications where chip evacuation flows in the direction of feed. Overall length is 2.5 inches with a 1 inch thread length, a shank diameter of 0.255 inches, and a square drive size of 0.191 inches. Thread limit is H1, indicating a close tolerance suitable for standard UNC fits.

This tap is used in machining, maintenance, and fabrication environments where 1/4-20 UNC threads are required in through holes. Typical applications include tapping steel, iron, aluminum, and similar materials by machinists, tool and die technicians, and maintenance mechanics. The straight flute geometry makes it appropriate for short-chipping materials. It is sold individually and is a standard bench or machine tap used in hand tapping, drill press, and tapping head setups.

Key Features

• 1/4-20 UNC thread form with right-hand thread direction
• Taper chamfer for gradual thread engagement in through-hole applications
• Four straight flutes suited for short-chipping materials
• High-speed steel construction for durability across a range of workpiece materials
• H1 thread limit for close-tolerance standard UNC fits
• Bright, uncoated finish — no coating buildup to affect thread dimensions

Compatibility

Designed as a standard replacement or stock tap for applications requiring 1/4-20 UNC internal threads; compatible with standard tap wrenches, drill press tapping attachments, and tapping heads sized for a 0.255-inch shank diameter.

Installation Notes

This tap should be installed and operated by qualified machinists or maintenance mechanics familiar with thread-cutting procedures. Secure the workpiece firmly before tapping and ensure the hole is drilled to the correct tap drill diameter for a 1/4-20 UNC thread. Apply appropriate cutting fluid for the workpiece material to extend tool life and improve thread finish. Do not force the tap if resistance increases sharply, as this may indicate chip packing or tool binding.