Cleveland C54391 Hand Tap 12-28 Unf Bottoming 4-flute Hss

Product Description

The CLEVELAND C54391 is a 12-28 UNF bottoming hand tap machined from high speed steel (HSS) with a bright uncoated finish. It carries a 4-flute straight flute geometry and a right-hand thread direction, making it suited for cutting internal threads in both blind and through-hole applications. The bottoming chamfer style allows threading to run as close to the bottom of a hole as possible, which is critical when full thread depth is needed near a closed end. Overall length is 2.375 inches with a thread length of 0.5 inches. The shank diameter measures 0.220 inches and the square drive measures 0.165 inches across. This tap is intended for use by machinists, maintenance technicians, and toolroom professionals working with standard hand tap wrenches or tap holders.

The C54391 is designed for threading operations in alloy steel, carbon steel, aluminum, and free-machining stainless steel. It is well suited for production and repair work in manufacturing, maintenance, and fabrication environments where 12-28 UNF internal threads are required. The H3 thread limit designation indicates a ground thread tolerance appropriate for standard Class 2B and 3B fit applications. Both blind hole and through-hole threading scenarios are supported.

Key Features

• Bottoming chamfer allows threading to within 1-2 pitches of a blind hole bottom
• 4-flute straight flute design provides balanced cutting action and good chip control in short-chipping materials
• H3 thread limit ground to suit Class 2B and 3B fit requirements
• High speed steel construction offers toughness and wear resistance across a range of workpiece materials
• Bright uncoated finish suitable for use with cutting oils and tapping fluids without coating interaction
• Right-hand thread direction, compatible with standard tap wrenches and hand tapping equipment

Compatibility

Designed for use in standard hand tapping operations requiring 12-28 UNF internal threads with a Class 2B or 3B fit in alloy steel, carbon steel, aluminum, and free-machining stainless steel workpieces.

Installation Notes

Installation is performed by machinists or maintenance technicians using a standard tap wrench or T-handle tap wrench sized to the 0.165-inch square drive. The workpiece should be secured and the pilot hole drilled and chamfered to the correct tap drill diameter for 12-28 UNF threads before tapping begins. Apply an appropriate cutting oil or tapping fluid to reduce friction and extend tap life, particularly in steel. Back off the tap periodically to break chips and prevent tap breakage in blind holes.