Osg 1664100 Straight Flute Tap 1-8 Unc Plug 3B Hss Left Hand

Product Description

The OSG 1664100 is a straight flute plug tap designed for cutting left-hand internal threads in a 1-8 UNC configuration. Built from high-speed steel (HSS) with a bright, uncoated finish, it features four flutes and a plug chamfer for gradual thread engagement. The H4 thread limit provides controlled oversize tolerance for plated or close-tolerance applications. At 5.125 inches overall length with a 2.5-inch thread length, this tap suits production and maintenance threading operations in machine shops and field repair environments. Licensed machinists and tooling specialists are the primary users of this tool.

This tap is intended for right-to-left, left-hand thread applications in a range of ferrous and non-ferrous materials. It performs in aluminum, cast aluminum, cast iron, low-carbon steel, medium-carbon steel, and high-carbon steel. The plug chamfer style makes it appropriate for through-hole threading where the tap can pass completely through the workpiece. It is part of the OSG Series 101L product line, which covers straight flute taps for standard threading needs across manual and CNC machine operations.

Key Features

• Left-hand thread direction for applications requiring reverse-thread fasteners or components
• Four-flute straight configuration moves chips axially, suited to through-hole threading
• Plug chamfer with gradual thread lead for controlled entry and reduced tap breakage risk
• H4 thread limit for controlled tolerance in plated or precision-fit assemblies
• High-speed steel construction provides durability across a broad range of workpiece materials
• Bright, uncoated finish allows direct inspection of tool wear and surface condition

Compatibility

Designed for cutting 1-8 UNC left-hand internal threads. Compatible workpiece materials include aluminum, cast aluminum, cast iron, low-carbon steel, medium-carbon steel, and high-carbon steel as specified by the manufacturer.

Installation Notes

This tap is installed and operated by machinists or tooling technicians using a tap wrench, tapping head, or CNC rigid tapping cycle. Ensure the spindle and workpiece are fully secured before beginning the threading operation. Because this is a left-hand tap, the spindle or wrench must rotate counterclockwise to advance the thread. Apply appropriate cutting fluid for the workpiece material to extend tool life and improve thread finish quality.