Osg 1012302 Straight Flute Tap 4-40 Unc Bottoming Hss

Product Description

The OSG 1012302 is a straight flute bottoming tap designed for threading 4-40 UNC holes in production and maintenance machining environments. Built from high-speed steel, it runs 3 flutes in a straight configuration, making it well suited for short-chipping materials where chip evacuation is predictable. The bottoming chamfer allows threading close to the bottom of blind holes where spiral-point or taper taps cannot reach. With an overall length of 1-7/8 inches and a thread length of 9/16 inches, the 1012302 fits standard tap holders and is appropriate for hand tapping or low-speed machine tapping operations.

This tap is intended for threading 4-40 UNC fastener holes in light manufacturing, repair, and toolroom settings. It carries a 2B and 3B class of fit designation, covering both standard commercial tolerances and closer-tolerance applications. The H2 thread limit provides consistent oversize control suited to most plated and unplated thread requirements. Right-hand thread orientation is standard for the vast majority of fastener applications in these size ranges.

Key Features

• Bottoming chamfer for threading to the base of blind holes
• 3 straight flutes optimized for short-chipping workpiece materials
• High-speed steel construction for general-purpose tap life and regrindability
• H2 thread limit for controlled oversize within 2B and 3B tolerance classes
• Right-hand thread direction, standard orientation
• Compact 1-7/8 inch overall length fits standard collet and tap handle setups

Compatibility

Designed for tapping aluminum, cast aluminum, cast iron, high-carbon steel, low-carbon steel, and medium-carbon steel. Compatible with standard 4-40 UNC thread forms per ASME B1.1. Fits tap holders and collets sized for this shank diameter in bench, drill press, and CNC tapping configurations.

Installation Notes

Installation and use should follow standard machinist practice: secure the workpiece fully before tapping and ensure the hole is drilled to the correct tap drill diameter for 4-40 UNC before engaging the tap. Apply appropriate cutting fluid for the workpiece material to extend tool life and improve thread finish. When machine tapping, use low spindle speeds consistent with the workpiece material and tap diameter. Reverse the tap periodically when hand tapping in deeper holes to break chips and prevent binding.