Osg 0135601 Spiral Flute Tap 4-40 Unc Bottoming Hss

Product Description

The OSG 0135601 is a spiral flute bottoming tap designed for cutting 4-40 UNC internal threads in blind holes. Made from vanadium high-speed steel with a steam oxide coating, it delivers consistent performance in ferrous and stainless steel applications. The 45-degree right-hand helix angle drives chips upward and out of the hole during tapping, reducing the risk of chip packing in blind bores. With an H2 thread limit and a 2B/3B class of fit, this tap produces threads that meet standard tolerance requirements for general-purpose fastener applications. Licensed machinists, tool-and-die makers, and maintenance technicians are the typical users.

This tap is suited for production and maintenance tapping in stainless steel, high-carbon steel, medium-carbon steel, and low-carbon steel. The bottoming chamfer geometry allows threading close to the bottom of blind holes, making it practical in tight-tolerance fixturing, instrumentation housings, and small-component assemblies where thread depth matters. The spiral flute design reduces cutting torque compared to straight-flute alternatives, which is an advantage in small-diameter tapping where tool breakage is a concern.

Key Features

• 45-degree right-hand spiral flute helix drives chips out of blind holes
• Bottoming chamfer for maximum thread depth in blind holes
• Vanadium high-speed steel construction for wear resistance in ferrous materials
• Steam oxide coating reduces friction and improves lubrication retention
• H2 thread limit for consistent 2B/3B class of fit compliance
• 3-flute configuration balances chip clearance and core strength at this diameter

Compatibility

Designed for cutting 4-40 UNC threads and rated for use in stainless steel, high-carbon steel, low-carbon steel, and medium-carbon steel workpieces. OSG Series 303.

Installation Notes

This tap is installed and operated by machinists using a tap wrench, tapping head, or CNC machining center with appropriate tap holders. Always apply cutting fluid compatible with the workpiece material before tapping to reduce heat and tool wear. Secure the workpiece firmly before tapping to prevent movement that can cause tap breakage. Inspect the tap for wear or chipping before each use, as small-diameter taps are especially vulnerable to breakage under side load or misalignment.