Osg 0139501 Spiral Flute Tap 5/8-18 Unf Bottoming 2B

Product Description

The OSG 0139501 is a spiral flute bottoming tap designed for cutting 5/8-18 UNF internal threads in ferrous materials. Built from vanadium high-speed steel with a steam oxide finish, it handles stainless steel, high-carbon steel, medium-carbon steel, and low-carbon steel. The 45-degree helix angle pulls chips up and out of the hole during tapping, reducing the risk of chip packing in blind or deep holes. With a 2B class of fit and H5 thread limit, it produces threads within standard tolerance for most fastener and mechanical assembly applications. The overall length measures 4.688 inches, making it compatible with standard tap holders for production and maintenance machining work.

This tap is suited for production shops, maintenance machinists, and toolroom applications where precise UNF threads are required in steel workpieces. The bottoming chamfer style allows threading to within a few pitches of the bottom of a blind hole, making it the correct choice when full thread depth close to the hole bottom is required. It carries a right-hand thread direction and right-hand flute direction, which is the standard configuration for most CNC and manual tapping operations on steel components.

Key Features

• Bottoming chamfer for maximum thread depth in blind holes
• 45-degree spiral flute helix angle for efficient chip evacuation on right-hand cuts
• Vanadium high-speed steel construction for improved wear resistance over standard HSS
• Steam oxide coating reduces friction and improves lubrication retention during tapping
• H5 thread limit and 2B class of fit for consistent, standardized thread tolerance
• 4 flutes for balanced cutting action in steel and stainless steel

Compatibility

Designed for tapping 5/8-18 UNF threads in stainless steel, high-carbon steel, medium-carbon steel, and low-carbon steel. Part of the OSG Series 303 spiral flute tap line.

Installation Notes

Install in a tap holder or collet rated for the 0.697-inch shank diameter before use. Power down and secure the workpiece before starting any tapping operation. Apply appropriate cutting fluid for the material being tapped, particularly when working with stainless steel, to reduce heat buildup and extend tap life. Do not force the tap if resistance is encountered — back off to clear chips before continuing.