Osg 1605401 Spiral Point Tap 4-40 Unc H2 Hss Oxide

Product Description

The OSG 1605401 is a spiral point tap designed to cut 4-40 UNC internal threads in through-hole applications. Manufactured from high-speed steel with a steam oxide coating, this plug chamfer tap drives chips forward ahead of the cutting zone, reducing clogging in production tapping operations. It features 2 flutes, an H2 thread limit for controlled tolerance, and a 2B/3B class of fit suitable for standard fastener thread requirements. The overall length is 1.875 inches with a shank diameter of 0.141 inches and a thread length of 0.319 inches. Right-hand cutting direction. Typically installed by machinists, tool and die makers, and maintenance technicians working with small-diameter threaded assemblies.

This tap is suited for through-hole tapping in a range of materials including low-carbon steel, medium-carbon steel, high-carbon steel, cast iron, aluminum, and cast aluminum. The spiral point design makes it well suited for production environments where through holes allow chips to be pushed clear rather than backed out. Plug chamfer provides a gradual lead-in over several threads, balancing cutting load across the entry threads. The 4-40 UNC thread form is commonly found in small instrument fasteners, electrical enclosures, and light mechanical assemblies.

Key Features

• Spiral point geometry pushes chips forward, reducing chip packing in through-hole tapping
• High-speed steel construction provides toughness across a broad range of workpiece materials
• Steam oxide coating improves lubricity and reduces friction during cutting
• H2 thread limit delivers controlled fit for 2B and 3B class of fit requirements
• Plug chamfer distributes cutting load over the lead threads for smooth entry
• Right-hand cutting direction, no coolant-through required

Compatibility

Compatible with workpiece materials including aluminum, cast aluminum, cast iron, low-carbon steel, medium-carbon steel, high-carbon steel, and hardened steel. Designed for 4-40 UNC through-hole tapping applications per OSG Series 105A.

Installation Notes

Tapping should be performed by a qualified machinist or maintenance technician using a properly sized tap wrench, tapping head, or machine spindle aligned with the pilot hole. Always use an appropriate cutting fluid or tapping compound for the workpiece material before beginning the cut. Ensure the pilot hole diameter is correct for 4-40 UNC before tapping to avoid tap breakage. Do not reverse direction under load without fully retracting the tap to clear chips.