Osg 2906400 Spiral Flute Tap 4-40 Unc Modified Bottoming

Product Description

The OSG 2906400 is a spiral flute tap designed to cut 4-40 UNC internal threads in a wide range of ferrous materials. It features three right-hand flutes with a 45-degree helix angle, which evacuates chips upward out of the hole — a critical advantage when tapping blind holes. The modified bottoming chamfer allows threading close to the bottom of a hole while still providing controlled entry. Ground to an H2 thread limit, this tap suits both 2B and 3B class-of-fit applications. The tool is manufactured from vanadium high-speed steel and left in a bright, uncoated finish. Overall length is 1.875 inches with a shank diameter of 0.141 inches.

This tap is suited for production and maintenance tapping of small-diameter holes in alloy steel, carbon steel, cast iron, stainless steel, die steel, and hardened steel. The 4-40 UNC thread form is widely used in precision instrumentation, electrical panels, small enclosures, and light mechanical assemblies. It is appropriate for hand tapping, tapping arms, and machine tapping operations where controlled chip removal from blind holes is required.

Key Features

• 45-degree right-hand spiral flutes for efficient upward chip evacuation in blind holes
• Modified bottoming chamfer allows threading close to the bottom of a hole
• H2 thread limit ground for 2B and 3B class-of-fit tolerance control
• Vanadium high-speed steel construction for durability across ferrous materials
• Bright uncoated finish suitable for use with standard cutting fluids
• Right-hand thread direction, no coolant-through requirement

Compatibility

Designed for cutting 4-40 UNC threads in alloy steel, carbon steel, cast iron, stainless steel, die steel, and hardened steel workpieces where 2B or 3B class-of-fit tolerances are required.

Installation Notes

This tap is installed and used by machinists, tool and die makers, and maintenance technicians. Before tapping, ensure the correct drill size for a 4-40 UNC thread is used and the workpiece is securely fixtured. Apply an appropriate cutting fluid for the material being tapped. When using in a machine tapping setup, verify spindle speed and feed rate are appropriate for the material to avoid tap breakage in this small diameter.