Osg 1650510308 Spiral Flute Tap 12-28 Unf Bottoming

Product Description

The OSG 1650510308 is a spiral flute bottoming tap designed for threading 12-28 UNF holes in a wide range of ferrous and non-ferrous metals. It is constructed from powdered metal and carries a V coating for improved wear resistance and lubricity during the tapping operation. With a 45-degree helix angle and 3 right-hand flutes, it evacuates chips up and out of blind holes, making it well suited for bottoming applications where thread depth is critical. The H3 thread limit and 2B class of fit make it appropriate for standard-tolerance internal threads. Overall length is 3.15 inches with a thread length of 0.33 inches and a tapping depth of 30 millimeters.

This tap is intended for use in machining and fabrication environments where blind-hole threading to close tolerances is required. It performs across a broad material range including low-carbon steel, medium-carbon steel, high-carbon steel, alloy steel, hardened steel, cast iron, aluminum, and cast aluminum. Stainless steel is also listed as a compatible material application. It is a fit for CNC machining centers, drill presses, and manual tapping operations in tool-and-die, maintenance, and production settings where 12-28 UNF threaded fastener holes are specified.

Key Features

• 45-degree helix angle promotes upward chip evacuation in blind holes
• Bottoming chamfer allows threading to the bottom of a blind hole
• V coating improves wear resistance and reduces friction during cutting
• Powdered metal construction provides consistent hardness and edge retention
• H3 thread limit with 2B class of fit for standard internal thread tolerances
• Right-hand flute direction compatible with conventional tapping spindle rotation

Compatibility

Designed for cutting 12-28 UNF internal threads in alloy steel, aluminum, cast aluminum, cast iron, hardened steel, high-carbon steel, low-carbon steel, medium-carbon steel, and stainless steel. Part of OSG Series 16505.

Installation Notes

Installation is performed by machinists and tool-and-die technicians. Ensure the workpiece is securely clamped and the tap is properly aligned with the drilled pilot hole before engaging the spindle. Use an appropriate cutting fluid or tapping compound for the workpiece material to extend tool life and improve thread quality. Do not exceed the recommended tapping depth and avoid forcing the tap if resistance increases unexpectedly, as bottoming taps have minimal lead chamfer and are susceptible to breakage if run dry or misaligned.