Osg 1172802 Straight Flute Tap 1/2-20 Unf Hss Plug

Product Description

The OSG 1172802 is a straight flute plug tap designed for cutting 1/2-20 UNF right-hand internal threads in a wide range of ferrous and non-ferrous materials. Built from high-speed steel (HSS), it features three straight flutes and a plug chamfer that distributes cutting load across several leading threads for controlled thread entry. The 3B class of fit and H3 thread limit ensure dimensional accuracy consistent with standard UNF fastener applications. With an overall length of 3.375 inches and a thread length of 1.656 inches, it fits standard tap holders and machines used in production and maintenance environments.

This tap is suited for through-hole and blind-hole tapping operations where chip flow out of the hole is not a concern and straight flute geometry provides adequate performance. Typical applications include tapping pre-drilled holes in aluminum, cast aluminum, cast iron, low-carbon steel, medium-carbon steel, and high-carbon steel workpieces. It is used by machinists, maintenance technicians, and tool-and-die professionals in job shops, production lines, and field repair settings. The plug chamfer makes it appropriate for starting a thread in a new hole as well as continuing a partially formed thread.

Key Features

• 1/2-20 UNF thread form, right-hand cut, 3B class of fit
• H3 thread limit for consistent dimensional control within UNF tolerance
• Three straight flutes suited for short-chipping materials including cast iron and aluminum alloys
• Plug chamfer with approximately 3-5 chamfered threads for gradual thread engagement
• High-speed steel construction provides wear resistance across the listed material applications
• 3.375 inch overall length fits standard tap wrenches, T-handle holders, and machine spindles

Compatibility

Designed for use in 1/2-20 UNF through-hole and blind-hole tapping operations in aluminum, cast aluminum, cast iron, high-carbon steel, low-carbon steel, and medium-carbon steel workpieces. No specific machine or system compatibility data was provided in the product input.

Installation Notes

Machinists and maintenance technicians should ensure the workpiece is securely fixtured and that the correct tap drill size for 1/2-20 UNF has been used before tapping. Apply cutting fluid or tapping compound appropriate to the workpiece material to extend tool life and improve thread quality. When tapping by hand, use a tap wrench with steady axial pressure and back off periodically to break chips. When machine tapping, verify spindle speed is appropriate for the material and HSS tooling before starting the cut.