Osg 1120401 Straight Flute Tap 1/4-28 Unf Plug Hss Oxide

Product Description

The OSG 1120401 is a straight flute tap designed to cut right-hand internal threads to the 1/4-28 UNF standard. Built from high-speed steel with an oxide finish, this 4-flute plug tap is suited for threading operations in a wide range of ferrous and non-ferrous materials. It carries a 3B class of fit and an H3 thread limit, which defines the allowable oversize tolerance on the tap to produce threads within standard tolerance ranges. With an overall length of 2.5 inches and a thread length of approximately 0.75 inches, it fits standard tap holders and hand-tap wrenches used in machining and fabrication shops.

The 1120401 is used in machine-shop, toolroom, and production environments where UNF threads are required in aluminum, cast aluminum, cast iron, low-carbon steel, medium-carbon steel, and high-carbon steel. The plug chamfer — typically 3 to 5 threads of lead — makes it appropriate for through-hole applications and for following a taper tap in blind-hole sequences. It is part of OSG Series 101, a standard-duty straight flute tap line intended for general-purpose threading.

Key Features

• 1/4-28 UNF right-hand thread form with 3B class of fit for standard tolerance internal threads
• H3 thread limit for controlled oversize tolerance, compatible with typical production threading requirements
• 4 straight flutes suited for short-chipping materials including cast iron, aluminum, and carbon steels
• Plug chamfer provides 3-5 threads of lead for through-hole threading and progressive blind-hole entry
• High-speed steel construction provides wear resistance across the listed material applications
• Oxide coating reduces friction and provides light lubrication retention during cutting

Compatibility

Designed for use in aluminum, cast aluminum, cast iron, low-carbon steel, medium-carbon steel, and high-carbon steel. Fits standard 1/4-inch tap holders and hand wrenches with a shank diameter of 0.255 inches and a square drive size of 0.191 inches.

Installation Notes

This tap is installed by machinists and tool-and-die professionals using a tapping machine, drill press with tapping head, or hand tap wrench. Before tapping, ensure the workpiece is securely fixtured and the pilot hole diameter matches the recommended drill size for 1/4-28 UNF threads. Apply appropriate cutting fluid for the workpiece material to extend tool life and improve thread finish. Reverse the tap periodically when hand-tapping to break chips and prevent tap breakage.