Hertel K008309AS Straight Flute Tap 1/4-20 Unc Hss

Product Description

The HERTEL K008309AS is a straight flute tap designed for cutting 1/4-20 UNC internal threads in a range of workpiece materials. Built from high-speed steel (HSS) with a bright/uncoated finish, this tap is suited for general-purpose threading in through-hole and blind-hole applications where chip evacuation is managed by the operator. The taper chamfer eases entry and thread-starting, reducing setup time. With 4 flutes and an H5 thread limit, it holds a 2B class of fit — the standard commercial tolerance for most fastener and threaded-insert applications. Overall length is 2.5 inches with a 1-inch thread length.

This tap is used in machine shops, maintenance facilities, and field fabrication settings wherever 1/4-20 UNC threaded holes are required. Straight flute geometry makes it appropriate for use in both hand tapping and machine tapping operations on ferrous and non-ferrous metals, plastics, and composite materials with moderate machinability. The right-hand thread direction and taper chamfer configuration make it a common first-choice tap for production and repair work. It is typically installed by machinists, millwrights, and maintenance technicians.

Key Features

• 1/4-20 UNC thread form with 4-flute straight geometry for stable, guided cutting action
• Taper chamfer (7-10 threads) eases entry and reduces starting torque
• H5 thread limit holds 2B class of fit for standard commercial threaded connections
• High-speed steel construction provides good wear resistance at moderate cutting speeds
• Bright/uncoated finish suits general-purpose applications without coating-related dimensional offset
• Right-hand thread direction; no coolant-through requirement simplifies setup

Compatibility

Designed as a standard replacement or production tap for any application requiring 1/4-20 UNC internal threads at a 2B class of fit. Compatible with standard tap handles, tapping heads, and CNC tapping attachments accepting a 0.255-inch shank diameter.

Installation Notes

Secure the workpiece fully before tapping to prevent movement during thread cutting. Use appropriate cutting fluid for the workpiece material to extend tap life and improve thread finish. In blind-hole applications, clear chips frequently to prevent tap breakage. When machine tapping, verify spindle speed and feed rate are matched to the tap diameter and workpiece material before engaging the cut.