Osg 2985701 Spiral Flute Tap 1/4-28 Unf Bottoming Hss

Product Description

The OSG 2985701 is a spiral flute bottoming tap designed for threading 1/4-28 UNF holes in aluminum and carbon steel workpieces. The right-hand, 3-flute spiral design with a 50-degree helix angle efficiently evacuates chips up and out of the hole, making it well suited for blind-hole applications where chip packing is a concern. The steam oxide coating reduces friction and provides a measure of corrosion resistance during storage and use. At 2.5 inches overall length, this tap fits standard tapping chucks and is ground to a 2B class of fit for general-purpose fastener threads. Installers and machinists specify bottoming taps when threads must run to the bottom of a blind hole with minimal relief.

This tap is intended for use in machine shops, maintenance facilities, and field repair environments where 1/4-28 UNF threads are required. It performs in aluminum and carbon steel at the material applications listed by the manufacturer. The bottoming chamfer style produces full threads immediately at the bottom of the hole, making it a second or third operation tap used after a taper or plug tap has started the thread. It is not designed for through-hole or continuous production tapping without appropriate cutting fluid.

Key Features

• Bottoming chamfer for threading to the bottom of blind holes
• 3-flute spiral design with 50-degree helix angle for upward chip evacuation
• High-speed steel construction for durability in aluminum and carbon steel
• Steam oxide coating reduces friction and inhibits corrosion
• 2B class of fit for standard general-purpose UNF threaded assemblies
• Right-hand thread and right-hand flute direction for conventional tapping

Compatibility

Designed for cutting 1/4-28 UNF right-hand threads in aluminum and carbon steel. Suitable for use in standard tapping chucks accepting a 0.255-inch shank diameter. Not rated for coolant-through applications.

Installation Notes

This tap should be installed and operated by a machinist or qualified tradesperson familiar with tapping procedures and tooling setup. Secure the workpiece and ensure the spindle or tapping arm is properly aligned before engaging the tap to prevent tap breakage. Use an appropriate cutting fluid or tapping compound for the material being threaded. As a bottoming tap, it should be used after a taper or plug tap has established the thread lead in the hole.