Hertel K011008AS Straight Flute Tap 4-40 Unc Hss

Product Description

The HERTEL K011008AS is a straight flute plug tap designed for cutting right-hand internal threads in a 4-40 UNC thread form. Manufactured from high-speed steel with a bright, uncoated finish, this tap is built for threading operations in ferrous and non-ferrous materials where coolant-through capability is not required. The H7 thread limit designation indicates a slightly oversize tap ground to produce threads at the upper tolerance range, accommodating plating allowances or tighter fits as needed. With a 0.003-inch oversize specification, it is well suited for applications requiring post-thread plating or anodizing. Machinists and maintenance professionals commonly select this tap for small-diameter machine screw threads in tooling, fixtures, and precision assemblies.

This tap is used in general machining, toolroom, and maintenance repair operations where 4-40 UNC threads are required. Its plug chamfer — typically 3 to 5 threads of lead — makes it appropriate for through-hole threading or for following a bottoming pass in blind holes. The 3-flute straight flute geometry provides chip clearance in shorter thread depths and maintains stability in small-diameter work. It is suited to manual tapping with a tap wrench or machine tapping in a drill press or CNC machining center at appropriate low-RPM feeds for the material being threaded.

Key Features

• 4-40 UNC right-hand thread form for standard machine screw applications
• Plug chamfer provides a gradual lead-in, suitable for through holes and most blind-hole work
• High-speed steel construction offers toughness and regrindability across a broad range of workpiece materials
• H7 thread limit with 0.003-inch oversize accommodates post-plating or anodizing allowances
• 3-flute straight flute design balances chip clearance and cutting edge strength at small diameters
• Bright uncoated finish allows for straightforward inspection of wear and regrind status

Compatibility

Designed as a standard replacement or stocking tap for any application requiring 4-40 UNC right-hand internal threads. Compatible with manual tap wrenches, tapping heads, and CNC rigid-tapping setups configured for small-diameter, fine-pitch UNC threading.

Installation Notes

This tap should be installed and operated by a qualified machinist familiar with small-diameter tapping procedures. Always secure the workpiece fully before beginning the threading operation, and use an appropriate cutting fluid for the workpiece material to extend tool life and improve thread quality. When machine tapping, verify that spindle speed and feed rate are set for the thread pitch and material before engaging the tap. Avoid excessive force — 4-40 is a small-diameter thread prone to breakage if the tap binds or is run dry.