Cleveland C59121 Spiral Point Extension Tap 5/16-18

Product Description

The CLEVELAND C59121 is a spiral point plug extension tap designed for threading 5/16-18 UNC internal threads in production and maintenance applications. Built from high speed steel with a bright/uncoated finish, this tap features a 2-flute spiral point geometry that pushes chips ahead of the cut, making it well suited for through-hole tapping. The H3 thread limit provides a controlled oversize tolerance for reliable fit with Class 2B threaded fasteners. At 6 inches overall length, the extended reach allows techs to thread holes in deep cavities or recessed locations that standard-length taps cannot access.

This extension tap is intended for use in metalworking, maintenance, and repair operations across a range of materials including steel, stainless steel, cast iron, aluminum, and other non-ferrous metals. The plug chamfer style requires only a small existing lead, making it appropriate for most standard through-hole threading work. It is commonly used by machinists, millwrights, and maintenance mechanics working with machine tools, drill presses, or tapping arms where extended reach is required.

Key Features

• Spiral point geometry drives chips forward ahead of the cutting edge for clean through-hole threads
• High speed steel construction provides wear resistance across ferrous and non-ferrous materials
• H3 thread limit delivers consistent Class 2B fit tolerance
• 6-inch overall length provides extended reach into deep or recessed holes
• Bright/uncoated finish suits general-purpose threading without coating-specific material restrictions
• Right-hand flute and right-hand thread direction for standard tap driver and machine use

Compatibility

Designed for threading 5/16-18 UNC through holes in steel, stainless steel, cast iron, aluminum, and other non-ferrous metals. Produces Class 2B internal threads compatible with standard 5/16-18 UNC fasteners.

Installation Notes

This tap should be installed and used by qualified machinists or maintenance mechanics familiar with proper tapping procedures. Always ensure the workpiece is securely clamped and the spindle or tapping arm is properly aligned before engaging the tap. Use an appropriate cutting fluid for the material being threaded to extend tap life and improve thread quality. Inspect the tap for wear or chipping before each use and never force a tap that has stopped advancing.