Osg 1661100 Straight Flute Tap 3/8-24 Unf Left Hand Hss

Product Description

The OSG 1661100 is a straight flute tap designed to cut left-hand internal threads in a range of ferrous and non-ferrous materials. Built from high-speed steel with a bright/uncoated finish, it produces 3/8-24 UNF threads to a 3B class of fit with an H3 thread limit. The plug chamfer style - with approximately 3 to 5 threads of lead - makes it well-suited for through-hole tapping applications where the tap can advance past the full thread depth. With 4 flutes and a 1-1/4 inch thread length, this tap delivers clean thread formation while chips clear along the straight flute geometry. It is part of the OSG 101L series.

This tap is intended for production and maintenance tapping of through holes in aluminum, cast aluminum, cast iron, low-carbon steel, medium-carbon steel, and high-carbon steel. The left-hand thread direction makes it a specific-application tool used when the assembly design requires a thread that resists counterclockwise loosening forces, or when a left-hand fastener is specified by the engineer. It is commonly used by machinists, tool and die makers, and maintenance technicians working on mechanical assemblies, fixtures, and equipment repair.

Key Features

• Left-hand thread direction for assemblies requiring reverse-thread fasteners
• 3/8-24 UNF thread form with 3B class of fit and H3 thread limit for precise tolerance control
• Plug chamfer with 4 straight flutes optimized for through-hole tapping
• High-speed steel construction suitable for a broad range of ferrous and non-ferrous workpiece materials
• Bright/uncoated finish compatible with standard cutting fluids and tapping compounds
• No coolant-through design - standard setup with external lubrication or flood coolant

Compatibility

Designed for tapping 3/8-24 UNF left-hand through holes in aluminum, cast aluminum, cast iron, low-carbon steel, medium-carbon steel, and high-carbon steel workpieces. Part of the OSG 101L series.

Installation Notes

Install in a tapping head, CNC machine, or hand tap wrench sized for the shank diameter of 0.381 inches. Always apply an appropriate cutting fluid or tapping compound for the workpiece material before and during tapping. Secure the workpiece firmly and ensure the tap is aligned perpendicular to the hole before starting the thread. For left-hand taps, verify the spindle or wrench rotation direction is reversed relative to standard right-hand tapping.