Import BDNA-20786 Straight Flute Tap 12-28 Unf Bottoming Hss

Product Description

The IMPORT BDNA-20786 is a straight flute bottoming tap designed for cutting 12-28 UNF internal threads in blind holes where full thread depth close to the bottom of the bore is required. Manufactured from high-speed steel with a gold oxide coating, it delivers reliable wear resistance and reduced friction during tapping operations. The 4-flute geometry provides good chip control in a range of workpiece materials. With an H3 thread limit, it produces threads within a consistent tolerance range suitable for standard UNF fastener assemblies. This tap is used by machinists, maintenance technicians, and trade professionals performing precision threading work on metal components.

This tap is suited for threading blind holes in ferrous and non-ferrous metals where a spiral-point or plug tap cannot achieve full thread engagement near the bottom of the bore. The bottoming chamfer engages nearly all the way to the base of the hole, making it the correct choice for close-tolerance work on repair jobs, production runs, and field maintenance applications requiring 12-28 UNF thread profiles. It is typically used as the final step in a two-tap or three-tap sequence following a taper or plug tap.

Key Features

• 12-28 UNF thread form for fine-pitch internal threading applications
• Bottoming chamfer allows thread cutting to the base of blind holes
• 4-flute straight design provides stable cutting geometry and chip clearance
• High-speed steel construction offers hardness and toughness for metal threading
• Gold oxide coating reduces friction and provides mild corrosion resistance during service
• H3 thread limit ensures consistent tolerance output for standard UNF fastener fit
• Right-hand thread direction matches standard fastener convention

Compatibility

Designed for use in any application requiring a 12-28 UNF right-hand internal thread, including blind-hole tapping in ferrous metals, aluminum, and similar machinable materials.

Installation Notes

Tapping operations should be performed with a calibrated tap wrench or tapping attachment using appropriate cutting fluid for the workpiece material. Ensure the workpiece is securely fixtured and the tap is started square to the hole to prevent tap breakage or thread misalignment. For blind holes, use a plug or taper tap to start the thread before finishing with this bottoming tap. Follow applicable shop safety practices and wear appropriate eye protection when performing threading operations.