Osg 1768501 Extension Tap 5/16-18 Spiral Flute Hss

Product Description

The OSG 1768501 is a spiral flute extension tap designed for threading operations in confined or deep-reach applications. It cuts a 5/16-18 UNC right-hand thread to a 3B class of fit and is manufactured from vanadium high-speed steel with a steam oxide finish. The modified bottoming chamfer allows threading close to the bottom of blind holes. With an overall length of 6 inches and a reduced shank diameter of 0.318 inches, this tap is built for use with standard tap holders on manual or machine tapping setups. Three flutes with a 30-degree helix angle promote chip evacuation in the materials this tool is rated for.

The OSG 1768501 is suited for threading carbon steel, hardened steel, and stainless steel workpieces in production machining, maintenance, and repair environments. The extended overall length gives machinists and tool and die technicians access to recessed holes and deep bores where standard-length taps cannot reach. It is appropriate for CNC machining centers, drill presses, and hand tapping operations where precise thread tolerance is required. Series 398 designation places it within a well-defined OSG product line used across general metalworking shops.

Key Features

• 5/16-18 UNC thread, right-hand direction, 3B class of fit for standard thread tolerance
• Modified bottoming chamfer for threading near the base of blind holes
• 30-degree helix angle with 3 right-hand flutes for efficient chip evacuation
• Vanadium high-speed steel construction for wear resistance in ferrous and stainless materials
• Steam oxide finish reduces friction and provides light corrosion resistance during storage and use
• Reduced shank at 0.318 inches diameter and 6 inches OAL for extended reach

Compatibility

Rated for use in carbon steel, hardened steel, and stainless steel. The reduced shank is compatible with standard tap holders and collet chucks sized for the 0.318-inch shank diameter.

Installation Notes

Tap installation should be performed by a qualified machinist or maintenance technician familiar with threading operations. Ensure the workpiece is securely clamped and the tap is properly aligned with the drilled pilot hole before beginning the threading cycle. Apply appropriate cutting fluid for the workpiece material to extend tool life and improve thread quality. Inspect the tap for wear or chipping before each use and never force a tap that has stopped turning, as breakage in the hole can make removal difficult.