Osg 1172800 Straight Flute Tap 1/2-20 Unf Hss Plug

Product Description

The OSG 1172800 is a straight flute tap designed to cut internal 1/2-20 UNF threads in a wide range of metals. It features three flutes and a plug chamfer, making it suited for through-hole tapping operations where chips can exit freely. Built from high-speed steel with a bright uncoated finish, it delivers reliable performance in production and maintenance environments. The H3 thread limit ensures the finished thread falls within the 3B class of fit tolerance, which is the standard for most general-purpose inch-series fastener applications. Machinists and maintenance technicians are the primary users of this tap.

This tap is intended for right-hand thread cutting in through-hole applications across a broad range of workpiece materials. It is well suited for aluminum, cast aluminum, cast iron, low-carbon steel, medium-carbon steel, and high-carbon steel. The plug chamfer style provides a gradual lead-in, distributing cutting load across the first several threads. It is commonly used in job shop, production machining, and general maintenance repair operations where 1/2-20 UNF threaded holes are required.

Key Features

• 1/2-20 UNF thread form with right-hand direction and H3 thread limit for 3B class of fit
• Three straight flutes for chip clearance in through-hole tapping
• Plug chamfer distributes cutting load across multiple lead threads
• High-speed steel construction provides good wear resistance across common ferrous and non-ferrous metals
• Bright uncoated finish suitable for use with standard cutting fluids and oils
• No coolant-through feature; standard external lubrication applies

Compatibility

Designed for through-hole tapping of 1/2-20 UNF threads in aluminum, cast aluminum, cast iron, low-carbon steel, medium-carbon steel, and high-carbon steel workpieces. OSG Series 103.

Installation Notes

Installation is performed by machinists using a tap wrench, tapping arm, or CNC machine with appropriate spindle speed and feed rate for the workpiece material. Secure the workpiece fully before tapping and apply a suitable cutting fluid or tapping oil to extend tool life and improve thread quality. Ensure the starting hole is drilled to the correct tap drill diameter for a 1/2-20 UNF thread before starting. Reverse the tap periodically when hand tapping to break chips and prevent tap breakage.