Cleveland C58440 Spiral Flute Tap 1/4-20 Unc Plug Hss

Product Description

The CLEVELAND C58440 is a spiral flute plug tap designed for blind hole threading in metalworking applications. Built from high speed steel with an oxide finish, this tap features a 1/4-20 UNC thread form, 3 right-hand flutes with a fast flute style, and a 52-degree helix angle. The steep helix angle lifts chips up and out of the hole during cutting, making it well suited for through-chip evacuation in blind hole work. With an H3 thread limit and 2B class of fit, the C58440 holds the dimensional tolerances required for standard UNC fastener threads. Licensed machinists, toolroom technicians, and maintenance professionals working in production or repair environments are the typical installers.

This tap is rated for use in aluminum, non-ferrous metals, and steel. The plug chamfer provides a gradual lead-in that distributes cutting forces across the first several threads, reducing tap breakage in moderate to harder materials. At 2.5 inches overall length and a 0.63-inch thread length, it fits standard tap holders and is packaged as a single unit. The 1093BO series from CLEVELAND is a general-purpose spiral flute line recognized in industrial tooling catalogs for consistent dimensional accuracy across production runs.

Key Features

• Spiral flute design with 52-degree helix angle for efficient chip evacuation in blind holes
• High speed steel construction for durability across aluminum, non-ferrous metals, and steel
• Plug chamfer for gradual thread engagement and reduced tap breakage
• H3 thread limit with 2B class of fit for standard UNC fastener thread tolerances
• Oxide finish provides light surface protection and reduces friction during cutting
• Right-hand flute and right-hand thread orientation for conventional machine tapping

Compatibility

Designed for use in standard tap holders accepting a 0.255-inch shank diameter. Suitable for blind hole threading operations in aluminum, non-ferrous metals, and steel workpieces requiring a 1/4-20 UNC 2B thread form.

Installation Notes

Installation is performed by machinists or toolroom technicians using a tapping machine, drill press, or CNC machining center with appropriate tap holder. Ensure the workpiece is securely fixtured and the pilot hole diameter matches the recommended tap drill size for 1/4-20 UNC threads before tapping. Use cutting fluid appropriate to the workpiece material to extend tap life and improve thread finish. Never reverse a spiral flute tap under power without confirming the machine and holder support reverse-feed operation.