Accupro T4677163 Spiral Flute Tap 4-40 3 Flute Hss Nitride

Product Description

The ACCUPRO T4677163 is a spiral flute tap designed for threading 4-40 unified coarse holes in ferrous and non-ferrous materials. It features a modified bottoming chamfer, allowing threads to be cut close to the bottom of a blind hole. The flute design — 3 right-hand spiral flutes at a 15-degree helix angle — evacuates chips upward out of the hole during cutting, reducing clogging in through and shallow blind applications. The body is ground from 3 percent vanadium high speed steel (HSS), which provides increased wear resistance and edge retention over standard M2 HSS. A nitride finish further extends tool life by reducing friction and improving lubricity at the cutting edge. This tap is intended for use by machinists, tool and die makers, and maintenance technicians.

The T4677163 is suited for threading small-diameter 4-40 holes in light fixtures, electronics enclosures, machine components, and precision assemblies. The modified bottoming chamfer makes it practical for blind holes where full thread engagement is required near the bottom. The slow spiral flute style is effective in softer steels, aluminum, brass, and plastics. With a thread limit of H3 and right-hand thread direction, it produces threads within standard tolerance for most 4-40 fastener applications. Coolant-through capability is not included in this design.

Key Features

• 4-40 thread size with right-hand thread and right-hand spiral flute direction
• Modified bottoming chamfer for threading close to the bottom of blind holes
• 3 spiral flutes at a 15-degree helix angle for upward chip evacuation
• 3 percent vanadium high speed steel construction for enhanced wear resistance
• Nitride finish reduces friction and extends cutting life
• H3 thread limit for consistent tolerance in standard 4-40 applications

Compatibility

Designed as a direct-use spiral flute tap for 4-40 threaded holes; compatible with standard tap holders and chucks sized for a 3.58 mm shank diameter.

Installation Notes

This tap is installed and operated by machinists or maintenance technicians using a tap wrench, tapping head, or CNC rigid tapping setup. Secure the workpiece before tapping and ensure the tap is properly aligned with the pilot hole to avoid breakage on this small diameter. Apply a suitable cutting fluid for the workpiece material to reduce heat and extend tool life. Never reverse the tap abruptly — back off periodically to break chips when hand-tapping in tough materials.