Osg 2940701 Spiral Flute Tap 1/4-28 Unf Modified Bottoming

Product Description

The OSG 2940701 is a spiral flute tap designed for cutting internal 1/4-28 UNF right-hand threads in a variety of ferrous materials. It features a 45-degree helix angle that efficiently evacuates chips upward and out of the hole, making it well suited for blind-hole tapping operations. Manufactured from vanadium high-speed steel and finished with a steam oxide coating, the 2940701 offers improved lubricity and corrosion resistance compared to uncoated HSS taps. The modified bottoming chamfer allows threads to be cut close to the bottom of a blind hole. Overall length is 2.5 inches with a thread limit of H11, indicating a controlled oversize fit for applications requiring a standard tolerance class.

This tap is intended for use in machine tapping operations across a range of ferrous workpiece materials including alloy steel, carbon steel, cast iron, stainless steel, die steel, and hardened steel. It fits standard tap holders and tapping heads used in machining centers, CNC mills, drill presses, and manual tapping arms. The spiral flute design and 45-degree helix make it particularly effective in blind holes where chip packing is a concern. Machinists and tool-and-die professionals working in production or maintenance environments will find this tap appropriate for precision threading tasks where close thread-limit control is required.

Key Features

• 1/4-28 UNF right-hand thread form for standard unified fine-pitch applications
• 45-degree right-hand spiral flutes for upward chip evacuation in blind holes
• Modified bottoming chamfer allows threading close to the bottom of a blind bore
• Vanadium high-speed steel construction for durability in ferrous materials including hardened steel
• Steam oxide coating improves lubricity and reduces galling
• H11 thread limit with oversize classification for controlled fit tolerance

Compatibility

Rated for use in alloy steel, carbon steel, cast iron, stainless steel, die steel, and hardened steel workpieces. Fits standard tap holders sized for a 0.255-inch shank diameter with a 0.191-inch square drive.

Installation Notes

This tap should be installed and driven by a qualified machinist using appropriate tapping fluid or cutting oil matched to the workpiece material. Always ensure the workpiece is securely fixtured and the tap is properly aligned with the drilled pilot hole before engaging. Consult the tap manufacturer or Machinery Handbook guidelines for correct tap drill size selection for 1/4-28 UNF threads. Inspect the tap for wear or chipping before each use, and never force a tap that has stalled — back it out to clear chips before continuing.