Osg 1140802 Straight Flute Tap 5/16-18 Unc Bottoming Hss

Product Description

The OSG 1140802 is a straight flute bottoming tap designed for cutting internal threads in a wide range of ferrous and non-ferrous metals. Built from high-speed steel, it produces a 5/16-18 UNC right-hand thread to a 2B class of fit with an H5 thread limit. The bottoming chamfer geometry allows threading close to the bottom of blind holes, making it a go-to tool for jobs where full thread depth is required. With 4 flutes and a 1-1/8 inch thread length, this tap delivers consistent chip formation and thread quality in production and maintenance environments alike. Licensed machinists, tool-and-die makers, and mechanical contractors all reach for this tap when tight tolerances in blind bores are on the ticket.

This tap is suited for threading blind holes in aluminum, cast aluminum, cast iron, high-carbon steel, low-carbon steel, and medium-carbon steel. Its straight flute design performs best in short-chipping materials where chips break cleanly and can be cleared from the flutes without spiraling. Typical applications include machine components, structural brackets, fluid fittings, and threaded inserts in repair and fabrication work. The Series 101 designation places it within OSG's standard catalog line of general-purpose hand and machine taps.

Key Features

• Bottoming chamfer for threading to the bottom of blind holes
• High-speed steel construction for use across a broad range of workpiece materials
• 5/16-18 UNC thread form to 2B class of fit with H5 thread limit
• 4 straight flutes optimized for short-chipping materials
• No coolant-through requirement - compatible with flood or manual lubrication setups
• Right-hand thread direction, suitable for standard spindle rotation

Compatibility

Designed for use in aluminum, cast aluminum, cast iron, high-carbon steel, low-carbon steel, and medium-carbon steel workpieces. Compatible with standard 5/16-18 UNC tapping operations on manual machines, CNC machining centers, and hand-tapping applications.

Installation Notes

This tap should be installed in a properly sized tap holder or chuck rated for the tool shank diameter before beginning any threading operation. Always ensure the workpiece is securely fixtured and that the correct tap drill size for 5/16-18 UNC has been used prior to tapping. Apply a suitable cutting fluid or tapping compound appropriate for the workpiece material to reduce heat and extend tool life. For blind-hole applications, clear chips frequently to prevent tap breakage and verify thread depth with a go/no-go gauge after threading.