Osg 1120502 Straight Flute Tap 1/4-28 Unf Bottoming Hss

Product Description

The OSG 1120502 is a straight flute bottoming tap designed for producing internal threads in a wide range of metals. Built from high-speed steel (HSS), it cuts 1/4-28 UNF right-hand threads to a 3B class of fit with an H3 thread limit, delivering consistent tolerance control in production and repair applications. The bottoming chamfer allows threading to the bottom of blind holes where taper or plug taps cannot reach. With 4 flutes and a 1-inch thread length, this tap suits machinists and maintenance techs working on precision thread work in ferrous and non-ferrous materials.

This tap fits residential and commercial maintenance, machine shop, and fabrication environments. It is suited for threading operations in aluminum, cast aluminum, cast iron, high-carbon steel, low-carbon steel, and medium-carbon steel. The straight flute geometry works well in short-chipping materials where chip evacuation through the flute is reliable. The 2-1/2-inch overall length accommodates standard tap handles and CNC tapping chucks for both manual and machine tapping setups.

Key Features

• Bottoming chamfer allows threading to the bottom of blind holes
• 1/4-28 UNF thread form with 3B class of fit and H3 thread limit for controlled tolerance
• 4-flute straight flute design optimized for short-chipping materials
• High-speed steel construction provides good wear resistance across a broad range of workpiece materials
• Right-hand thread direction, compatible with standard tapping equipment
• No coolant-through requirement, simplifying setup in manual and light-duty machine applications

Compatibility

Designed for use in aluminum, cast aluminum, cast iron, high-carbon steel, low-carbon steel, and medium-carbon steel workpieces. Part of OSG Series 101.

Installation Notes

Installation is performed by machinists or maintenance technicians using a standard tap handle, T-handle, or CNC tapping chuck. Ensure the workpiece is securely fixtured and the tap is aligned perpendicular to the hole before engaging. Apply appropriate cutting fluid for the workpiece material to extend tap life and improve thread quality. For blind holes, verify hole depth is sufficient to accommodate the thread length plus the non-cutting chamfer length before tapping.