Osg 3142903 Straight Flute Tap 4-40 Unc Bottoming

Product Description

The OSG 3142903 is a straight flute tap designed for cutting internal threads in bottoming applications where full thread depth close to the base of a blind hole is required. Built from cobalt high-speed steel and finished with a nitride coating, the tap resists wear and handles elevated cutting temperatures better than standard HSS tooling. The 4-flute straight flute geometry provides rigidity and a clean thread form in materials such as plastics. It cuts a 4-40 UNC right-hand thread to a 2B class of fit, which is the standard tolerance for most general fastener applications. Licensed machinists, toolmakers, and maintenance technicians use this tap for precision threading in small-diameter work.

This tap is suited for threading 4-40 UNC holes in plastic workpieces in both production and repair environments. The bottoming chamfer - typically 1 to 2 thread leads - allows the tap to reach near the bottom of a blind hole, making it the correct choice when a plug or taper tap cannot produce a full thread length. It is commonly used with a tapping head, tap wrench, or CNC rigid tapping cycle where coolant-through tooling is not required.

Key Features

• Cobalt HSS construction for improved heat and wear resistance over standard HSS
• Nitride coating reduces friction and extends tool life in abrasive materials
• Bottoming chamfer enables full thread depth in blind holes
• 4 straight flutes provide rigidity and clean thread form in plastics
• 2B class of fit meets standard tolerance requirements for most UNC fastener applications
• Right-hand thread direction compatible with conventional tapping operations

Compatibility

Designed for cutting 4-40 UNC internal threads in plastic materials; suitable for use with standard tap wrenches, tapping heads, and CNC tapping cycles that accept round-shank taps of the appropriate shank diameter.

Installation Notes

This tap is installed and used by machinists and maintenance technicians performing threading operations. Always secure the workpiece and use a correctly sized and drilled tap drill hole before beginning the tapping operation. Apply appropriate cutting fluid for the material being tapped even when coolant-through tooling is not in use. Inspect the tap for wear or chipping before each use - a damaged tap can produce undersized or malformed threads.