Osg 1025802 Straight Flute Tap 12-28 Unf Plug H3 Hss

Product Description

The OSG 1025802 is a straight flute plug tap designed for cutting internal threads in a wide range of ferrous and non-ferrous materials. It produces a 12-28 UNF right-hand thread with a plug chamfer, making it suitable for through-hole and most blind-hole applications where some lead-in clearance is available. Built from high-speed steel, it delivers reliable edge retention across production and maintenance tapping operations. The tap features 4 flutes and is ground to an H3 thread limit, supporting both 2B and 3B class-of-fit tolerances. Overall length is 2-5/8 inches with a 15/16-inch thread length.

This tap is used in machine shop, maintenance, repair, and fabrication settings where 12-28 UNF threads are required. It is well suited for tapping aluminum, cast aluminum, cast iron, low-carbon steel, medium-carbon steel, and high-carbon steel workpieces. Typical applications include threading holes in fixtures, brackets, fastener repairs, and component assemblies across automotive, industrial, and general metalworking environments. Coolant-through is not supported, so standard flood or manual lubrication applies.

Key Features

• 12-28 UNF thread form, right-hand cut, H3 thread limit
• Plug chamfer provides 3-5 threads of lead-in for versatile through-hole and blind-hole use
• 4 straight flutes for chip clearance in the supported material range
• High-speed steel construction for consistent edge retention in carbon and alloy steels as well as aluminum
• Supports both 2B and 3B class-of-fit tolerances in a single tool
• Compact 2-5/8-inch overall length suits standard tap handles and CNC turrets

Compatibility

Designed for tapping 12-28 UNF threaded holes in aluminum, cast aluminum, cast iron, low-carbon steel, medium-carbon steel, and high-carbon steel. Compatible with standard tap holders, T-handle wrenches, and CNC rigid-tapping chucks sized for this shank diameter.

Installation Notes

Tapping should be performed by a qualified machinist or maintenance technician following standard threading practices. Ensure the workpiece is securely fixtured and the tap is properly aligned with the drilled pilot hole before applying torque. Apply an appropriate cutting fluid or tapping compound for the workpiece material to extend tool life and improve thread finish. Never exceed the recommended feed rate for the tap size, and back off periodically to break chips when working in blind holes.