Osg 2940401 Spiral Flute Tap 1/4-28 Unf Modified Bottoming

Product Description

The OSG 2940401 is a spiral flute tap designed for cutting internal right-hand threads to the 1/4-28 UNF standard. Built from vanadium high-speed steel with a steam oxide coating, it delivers hardness retention and reduced friction during tapping operations. The modified bottoming chamfer allows threading close to the bottom of blind holes, making it well-suited for tight-tolerance work. With a 45-degree helix angle and 3 right-hand flutes, the tool efficiently evacuates chips upward out of the hole during the cut. Licensed machinists, tool-and-die makers, and maintenance technicians are the primary users.

This tap is intended for use in blind and through-hole applications requiring UNF fine-thread profiles. Its material compatibility spans a wide range of metals, including alloy steel, carbon steel, cast iron, stainless steel, die steel, and hardened steel. The H5 thread limit designation indicates a close-tolerance fit suitable for precision assemblies. It fits standard tap holders and is appropriate for both hand tapping and machine tapping setups where controlled feed is maintained.

Key Features

• Modified bottoming chamfer for threading close to the bottom of blind holes
• 45-degree helix angle with 3 spiral flutes for upward chip evacuation
• Vanadium high-speed steel construction for hardness and wear resistance
• Steam oxide coating reduces friction and provides mild corrosion resistance
• H5 thread limit for close-tolerance UNF thread production
• Compatible with a broad range of ferrous materials including hardened steel

Compatibility

Designed for cutting 1/4-28 UNF right-hand internal threads in alloy steel, carbon steel, cast iron, stainless steel, die steel, and hardened steel workpieces. Part of OSG Series 290.

Installation Notes

This tap is installed by machinists or maintenance technicians using a standard tap wrench or machine tap holder. Ensure the workpiece is securely clamped and the pilot hole diameter is correctly sized for a 1/4-28 UNF thread before starting. Apply appropriate cutting fluid for the workpiece material to extend tool life and improve thread quality. Do not force the tap if resistance increases unexpectedly, as breakage in blind holes can be difficult to recover from.