Hertel K008376AS 5/16-18 Unc Bottoming Tap 4 Flutes Hss

Product Description

The HERTEL K008376AS is a straight flute bottoming tap designed for cutting 5/16-18 UNC internal threads in through-holes and blind holes where threads must extend close to the bottom. Manufactured from high-speed steel (HSS) with a bright/uncoated finish, this tap delivers consistent thread geometry across a wide range of materials including mild steel, aluminum, and plastics. The bottoming chamfer configuration — typically 1 to 2 lead threads — allows the tap to thread nearly to the bottom of a blind hole. With 4 flutes and an H1 thread limit, it holds tight tolerances for precision fastener applications. Overall length is 2-23/32 inches with a 1-1/8 inch thread length.

This tap is suited for manual or machine tapping operations in job shop, maintenance, and production environments. The 5/16-18 UNC thread form is one of the most common coarse-thread sizes in general mechanical assembly, making this tap a standard tool for machinists, maintenance technicians, and toolroom personnel. The straight flute design works best in short-chipping materials where chip evacuation back out of the hole is not a primary concern. It is typically used after a plug or taper tap has started the thread in a blind hole.

Key Features

• Bottoming chamfer for threading close to the bottom of blind holes
• 4 straight flutes for rigidity and consistent chip control in short-chipping materials
• H1 thread limit for tight tolerance control on finished thread fit
• High-speed steel construction provides good wear resistance across common workpiece materials
• Bright/uncoated finish — no coating buildup that could affect thread dimensions
• Right-hand thread direction, standard for 5/16-18 UNC fastener applications

Compatibility

Designed as an OEM-style replacement or direct equivalent for standard 5/16-18 UNC bottoming tap applications. Shank diameter is 0.3180 inches and square size is 0.2380 inches, compatible with standard tap wrenches and holders sized for this shank class.

Installation Notes

Always secure the workpiece and ensure the tap is properly aligned before applying torque — misalignment is a leading cause of tap breakage. Use appropriate cutting fluid for the workpiece material to reduce friction and extend tool life. In machine tapping, verify that the tapping head or spindle is set to the correct feed rate for 18 TPI before engaging. Inspect the pre-drilled hole diameter against the recommended tap drill size for 5/16-18 UNC before tapping.