Osg 1681000 Straight Flute Tap 1/2-28 Unef Bottoming Hss

Product Description

The OSG 1681000 is a straight flute bottoming tap designed for cutting right-hand internal threads to the 1/2-28 UNEF standard. Built from high-speed steel with a bright uncoated finish, it features 4 flutes and an H3 thread limit for controlled tolerance fits. With an overall length of 3-3/8 inches and a thread length of 1-21/32 inches, this tap is sized for production and maintenance threading work in both shop and field environments. The bottoming chamfer allows threading to the bottom of blind holes where other chamfer styles cannot reach. It is installed by machinists, toolmakers, and maintenance mechanics using a standard tap wrench or machine tapping setup.

The OSG 1681000 is suited for threading aluminum, cast aluminum, cast iron, high-carbon steel, low-carbon steel, and medium-carbon steel. The 1/2-28 UNEF thread form is common in precision assemblies, firearm barrels, and instrumentation hardware where a finer thread pitch than standard UNF is required. This tap fits into the OSG 101N series and is appropriate for both manual tapping and light machine tapping applications in job shop and production settings.

Key Features

• Bottoming chamfer allows threading to the full depth of blind holes
• 4 straight flutes for clean chip evacuation in short-chipping materials
• H3 thread limit for consistent tolerance control in close-fit assemblies
• High-speed steel construction provides durability across a wide range of workpiece materials
• Bright uncoated finish suitable for use with standard cutting fluids
• Right-hand thread direction, no coolant-through requirement

Compatibility

Designed for threading 1/2-28 UNEF right-hand internal threads in aluminum, cast aluminum, cast iron, high-carbon steel, low-carbon steel, and medium-carbon steel workpieces. Part of the OSG 101N series.

Installation Notes

This tap is installed by machinists or maintenance mechanics using a tap wrench, tapping head, or CNC tapping cycle. Ensure the workpiece is securely fixtured and the tap is aligned perpendicular to the hole before starting. Apply an appropriate cutting fluid for the workpiece material to reduce heat and extend tool life. Inspect the tap for wear or chipping before each use and never force a tap that has seized in the hole.