Osg 1661500 Straight Flute Tap 7/16-20 Unf Plug Hss Left Hand

Product Description

The OSG 1661500 is a straight flute plug tap designed for cutting 7/16-20 UNF internal left-hand threads in a variety of ferrous and non-ferrous materials. Built from high-speed steel with a bright uncoated finish, it is suited for production and maintenance machining environments where left-hand thread creation is required. The plug chamfer distributes cutting load across the first few leading threads, making it a practical choice for through-hole applications. With an H3 thread limit tolerance and 4 flutes, this tap provides stable chip control and consistent thread geometry. Machinists, tool-and-die makers, and maintenance technicians working with manual or CNC tapping equipment are the primary users.

This tap is applied in tapping operations across materials including aluminum, cast aluminum, cast iron, low-carbon steel, medium-carbon steel, and high-carbon steel. It is part of the OSG 101L series and is built specifically for left-hand thread applications where standard right-hand taps cannot be used. Typical scenarios include reverse-thread fastener installations, anti-loosening assemblies, and specialty fixture work. The bright uncoated finish makes it well suited for aluminum and softer metals where coated taps may not be necessary.

Key Features

• Left-hand thread direction for reverse-thread applications
• 7/16-20 UNF thread form with H3 tolerance class for consistent fit
• Plug chamfer for through-hole tapping with distributed cutting load
• High-speed steel construction for durability across multiple materials
• 4 straight flutes for stable cutting and chip clearance
• Bright uncoated finish suited for aluminum and carbon steel applications

Compatibility

Designed for use in tapping applications involving aluminum, cast aluminum, cast iron, low-carbon steel, medium-carbon steel, and high-carbon steel where a 7/16-20 UNF left-hand internal thread is required. Compatible with standard tap holders and manual tapping equipment accepting the corresponding shank diameter.

Installation Notes

Tapping operations should be performed by qualified machinists following standard shop safety procedures. Secure the workpiece firmly and ensure proper alignment between the tap and the drilled pilot hole before starting the operation. Use an appropriate cutting fluid for the material being tapped to extend tap life and improve thread finish. When using left-hand taps in power equipment, confirm the spindle rotation direction is set to left-hand before engaging the tap.