Osg 1012300 Straight Flute Tap 4-40 Unc Bottoming Hss

Product Description

The OSG 1012300 is a straight flute bottoming tap designed for cutting 4-40 UNC internal threads in a wide range of ferrous and non-ferrous materials. Built from high-speed steel with a bright/uncoated finish, this tap features 3 flutes and an H2 thread limit, providing controlled tolerances suited to both 2B and 3B class of fit applications. It has an overall length of 1-7/8 inches and a thread length of 9/16 inches, making it a compact, precision tool for threading through blind holes where a bottoming chamfer is required. Licensed machinists, maintenance technicians, and tool-and-die professionals rely on this tap for accurate thread forming in production and repair settings.

This tap is well suited to tapping aluminum, cast aluminum, cast iron, low-carbon steel, medium-carbon steel, and high-carbon steel. The bottoming chamfer style allows threading to the bottom of blind holes, making it a common choice for close-tolerance assemblies in mechanical, industrial, and maintenance-repair-operations work. It carries a right-hand thread direction and is part of OSG Series 102. Its small 4-40 size makes it especially useful in precision instrument work, electronics enclosures, and light mechanical assemblies where fine thread engagement is critical.

Key Features

• Bottoming chamfer for threading to the bottom of blind holes
• High-speed steel construction for durability across ferrous and non-ferrous materials
• H2 thread limit supports tight 2B and 3B class of fit tolerances
• 3-flute design provides chip clearance and stable cutting action in small-diameter tapping
• 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 right-hand internal threads in aluminum, cast aluminum, cast iron, low-carbon steel, medium-carbon steel, and high-carbon steel workpieces. Compatible with standard tap holders and machine tool collets sized for a 0.141-inch shank diameter.

Installation Notes

Tapping operations should be performed by a qualified machinist or maintenance technician using a properly sized tap holder or tapping head. Always drill the correct tap drill size and clear chips from the hole before starting. Apply an appropriate cutting fluid for the workpiece material to reduce friction and extend tool life. Do not force the tap into the hole; back off periodically to break chips and prevent tap breakage.