Osg 1066400 Straight Flute Tap 4-40 Unc Bottoming Hss

Product Description

The OSG 1066400 is a straight flute bottoming tap designed for cutting internal 4-40 UNC threads in ferrous and non-ferrous metals. With 2 flutes and a bottoming chamfer, this tap threads holes to near full depth, making it the right choice for blind holes where thread engagement must start close to the bottom. Manufactured from high-speed steel with a bright, uncoated finish, it offers reliable cutting performance across a broad range of workpiece materials. Overall length is 1-7/8 inches with a thread length of 9/16 inches. This tap is used by machinists, maintenance technicians, and fabricators working in production and repair environments.

The 1066400 is suited for tapping 4-40 UNC threads in aluminum, cast aluminum, cast iron, high-carbon steel, low-carbon steel, and medium-carbon steel. Its straight flute design is appropriate for through-holes and short blind holes where chips can be pushed down or cleared manually. The 2B and 3B class of fit coverage makes it versatile for both standard commercial and precision thread applications. Typical install scenarios include instrument frames, electrical enclosures, small mechanical assemblies, and repair work on threaded fastener holes in light steel and aluminum components.

Key Features

• Bottoming chamfer allows threading to near full depth in blind holes
• 4-40 UNC thread form with H2 thread limit for consistent fit tolerances
• High-speed steel construction for durability across steel and aluminum materials
• Bright uncoated finish suitable for use with standard cutting fluids
• Right-hand thread direction, 2 straight flutes
• No coolant-through requirement - compatible with manual or standard machine tapping

Compatibility

Designed as a standard OEM-style replacement or production tap for 4-40 UNC applications across aluminum, cast aluminum, cast iron, high-carbon steel, low-carbon steel, and medium-carbon steel workpieces.

Installation Notes

This tap is installed by machinists or maintenance technicians using a tap wrench, tapping head, or CNC machine tool. Always use an appropriate cutting fluid for the workpiece material and clear chips periodically to prevent tap breakage. Ensure the pilot hole is drilled to the correct tap drill diameter for 4-40 UNC before threading. Secure the workpiece fully before tapping to prevent movement that could break the tap or misalign the thread.