Cleveland C55031 Straight Flute Hand Tap 1-3/8"-12 UNF Plug 6 Flutes

Cleveland C55031 Straight Flute Tap

The Cleveland C55031 is a straight flute hand tap designed for cutting 1-3/8"-12 UNF threads in a variety of materials. It suits machinists and maintenance technicians who need to create internal threads for fine-pitch fasteners. The H4 thread limit targets a Class 2B fit for standard assemblies. This tool is not for automated high-volume tapping operations or for users requiring coated cutting geometry.

High-Speed Steel Construction and Plug Chamfer

The tap is manufactured from high-speed steel with a bright, uncoated finish for general-purpose cutting performance. Its straight flute design with six flutes provides chip clearance in through-hole and blind-hole applications. The plug chamfer offers a moderate lead-in for easier starting alignment by hand. The 3-inch thread length and 6 1/16-inch overall length give adequate reach for common workpieces. The right-hand cut orientation matches standard fastener threads.

UNF Thread Standard and Drill Size Requirement

This tap produces Unified National Fine threads with a 12 threads-per-inch pitch diameter. The fine pitch limits material removal rate compared to coarse series taps, requiring more torque per revolution. A precise 75 percent thread drill size of 1.2938 inches must be used to achieve the correct Class 2B fit. The fixed H4 limit means the tap cannot compensate for hole size variation or provide oversize threads for plating allowances.