Osg 0138301 Spiral Flute Tap 7/16-14 Unc Bottoming Hss

Product Description

The OSG 0138301 is a spiral flute bottoming tap designed to cut right-hand internal threads in through-holes and blind holes where threads must extend close to the bottom. Manufactured from vanadium high-speed steel with a steam oxide coating, this tap handles stainless steel, high-carbon steel, low-carbon steel, and medium-carbon steel. The 45-degree helix angle drives chips up and out of the flute during the cut, reducing the risk of chip packing in deep or tight holes. At 3.156 inches overall length with a 0.571-inch thread length, it is sized for standard machine tapping setups used by machinists and tool-and-die tradespeople.

This tap is intended for production and maintenance tapping of 7/16-14 UNC threads across a range of ferrous materials. The bottoming chamfer — typically 1 to 2 thread leads — allows the tap to cut threads nearly to the bottom of a blind hole, making it the correct choice when thread engagement depth is critical. It suits CNC machining centers, drill presses with tapping attachments, and manual tapping operations. The H3 thread limit provides a controlled oversize fit appropriate for standard tolerance Class 2B and Class 3B nut-fit threading applications.

Key Features

• Bottoming chamfer for full thread depth in blind holes
• 45-degree right-hand spiral flute evacuates chips away from the cutting zone
• Vanadium high-speed steel construction for extended tool life in ferrous materials
• Steam oxide coating reduces friction and improves lubrication retention
• H3 thread limit for controlled Class 2B and 3B fit tolerance
• No coolant-through design — compatible with standard flood or brush-applied cutting fluid

Compatibility

Designed for tapping 7/16-14 UNC right-hand threads in stainless steel, high-carbon steel, low-carbon steel, and medium-carbon steel workpieces. OSG Series 303.

Installation Notes

Install and remove taps using a proper tap wrench or tapping chuck rated for the shank diameter — never use pliers or adjustable wrenches on the square drive. Secure the workpiece fully before tapping and align the tap perpendicular to the drilled hole to avoid tap breakage or thread misalignment. Apply cutting fluid rated for the workpiece material before and during tapping. When tapping blind holes with a bottoming tap, advance in short increments and back off periodically to break chips, especially in stainless steel.