Osg 1661900 Straight Flute Tap 1/2-20 Unf Left Hand Hss

Product Description

The OSG 1661900 is a straight flute tap designed to cut 1/2-20 UNF internal threads in a left-hand direction. Built from high-speed steel with a bright/uncoated finish, it features a plug chamfer for general-purpose through-hole and blind-hole tapping applications. The H3 thread limit ensures consistent tolerance control in production environments. With 4 flutes and a 3B class of fit, this tap delivers reliable thread form across a range of ferrous and non-ferrous materials. It is intended for use by machinists and tool and die professionals working with manual or CNC tapping equipment.

This tap is suited for tapping operations in aluminum, cast aluminum, cast iron, high-carbon steel, low-carbon steel, and medium-carbon steel. The left-hand thread configuration makes it the appropriate choice for applications where standard right-hand threads would loosen under operational torque, or where left-hand fasteners are specified by design. The plug chamfer provides a moderate lead-in, making it functional in both through-hole and sufficiently deep blind-hole setups.

Key Features

• Left-hand thread direction for applications requiring reverse-thread fasteners
• Plug chamfer for versatile use in through-holes and deep blind holes
• H3 thread limit for consistent tolerance and fit in production tapping
• 3B class of fit for standard internal thread tolerance compliance
• High-speed steel construction provides durability across a broad material range
• 4-flute design for balanced cutting action and chip clearance

Compatibility

Designed for tapping 1/2-20 UNF left-hand threads in aluminum, cast aluminum, cast iron, high-carbon steel, low-carbon steel, and medium-carbon steel workpieces.

Installation Notes

This tap should be installed and operated by qualified machinists familiar with tapping procedures and toolholding requirements. Ensure the workpiece is securely fixtured and the tap is properly aligned before beginning the tapping cycle. Use an appropriate cutting fluid or tapping compound matched to the workpiece material to extend tool life and improve thread quality. Do not reverse a tap that has broken or jammed without first relieving cutting pressure to avoid fracture.