Osg 1430205 Spiral Flute Tap 1/4-28 Unf Tin Hss

Product Description

The OSG 1430205 is a spiral flute plug tap designed for cutting 1/4-28 UNF internal threads in a range of ferrous and non-ferrous materials. Built from high-speed steel (HSS) with a titanium nitride (TiN) coating, it delivers extended tool life and reduced friction during the threading operation. The three right-hand spiral flutes pull chips up and out of the hole, making this tap well suited for blind-hole applications where chip evacuation is critical. With a 50-degree helix angle and an H3 thread limit, it holds tolerance to a 3B class of fit. Overall length is 2.5 inches with a thread length of 0.645 inches. This tool is installed by machinists, tool-and-die makers, and maintenance technicians working in production or job-shop environments.

This tap is appropriate for use 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 taper — requires a pre-drilled hole and is the standard choice for through-holes or blind holes with sufficient depth. It belongs to OSG Series 107, a line of general-purpose spiral flute taps suited for both manual and CNC tapping operations in light to medium production work.

Key Features

• 1/4-28 UNF right-hand thread, H3 thread limit, 3B class of fit
• Three right-hand spiral flutes at a 50-degree helix angle for upward chip evacuation in blind holes
• TiN coating reduces friction and increases wear resistance compared to uncoated HSS
• Plug chamfer provides smooth thread entry and is suitable for both through and blind-hole applications
• 2.5-inch overall length with 0.645-inch thread length and 0.255-inch shank diameter
• No coolant-through design; suitable for conventional flood or hand-applied cutting fluid

Compatibility

Designed as a standard 1/4-28 UNF spiral flute plug tap compatible with manual tap handles, tapping heads, and CNC rigid-tapping setups that accept a 0.255-inch shank diameter. Rated for use in aluminum, cast aluminum, cast iron, low-carbon steel, medium-carbon steel, and high-carbon steel per OSG Series 107 specifications.

Installation Notes

Use the correct tap drill size for a 1/4-28 UNF thread before tapping; an undersized hole will overload the tap and risk breakage. Apply appropriate cutting fluid for the workpiece material — sulfurized oil for steel, a light petroleum-based fluid or kerosene for aluminum. When tapping on a CNC machine, confirm spindle RPM and feed rate match the tap pitch to avoid thread damage or breakage. Never reverse a broken tap in the hole without appropriate extraction tooling.