Osg 1066300 Straight Flute Tap 4-40 Unc 2 Flute Hss

Product Description

The OSG 1066300 is a straight flute tap designed for cutting 4-40 UNC internal threads in a wide range of ferrous and non-ferrous materials. Built from high-speed steel with a bright, uncoated finish, this tap features a plug chamfer for general-purpose through-hole and blind-hole tapping. It carries a 2B and 3B class of fit with an H2 thread limit, making it suitable for standard and close-tolerance threaded fastener applications. The overall length is 1-7/8 inches with a thread length of 9/16 inches. Licensed machinists, tool-and-die makers, and maintenance technicians are the primary users of this tap in production and repair environments.

This tap is well suited for tapping operations in aluminum, cast aluminum, cast iron, low-carbon steel, medium-carbon steel, and high-carbon steel. The straight flute design works effectively in through-hole applications where chip evacuation is straightforward and cutting fluid can reach the cutting zone. It is a common selection for small-fastener thread work on machined components, fixtures, and assemblies in both job-shop and production settings.

Key Features

• 4-40 UNC thread form with 40 threads per inch for fine small-diameter fastener applications
• High-speed steel construction provides durability across a broad range of workpiece materials
• Plug chamfer (typically 3-5 thread lead) suits both through-hole and moderately deep blind-hole tapping
• 2B and 3B class of fit with H2 thread limit for standard and close-tolerance thread requirements
• Right-hand thread direction, the standard orientation for general tapping operations
• Bright, uncoated finish - compatible with most cutting oils and tapping fluids without coating compatibility concerns

Compatibility

Rated for use in aluminum, cast aluminum, cast iron, low-carbon steel, medium-carbon steel, and high-carbon steel. Designed as an OEM-style straight flute tap for standard 4-40 UNC tapping applications where a plug-style entry and H2 thread limit are specified.

Installation Notes

This tap is installed and driven by a machinist or maintenance technician using a tap wrench, tapping head, or CNC rigid-tap cycle. Before tapping, drill the correct tap drill size for a 4-40 UNC thread and ensure the workpiece is securely fixtured. Apply an appropriate cutting fluid or tapping compound for the workpiece material to extend tap life and improve thread finish. Do not force the tap if resistance increases suddenly - back off to break the chip, then continue.