Osg 1748301 Spiral Flute Tap 4-40 Unc Bottoming Hss

Product Description

The OSG 1748301 is a spiral flute bottoming tap designed for cutting internal threads in blind holes where full thread engagement near the bottom of the bore is required. Ground from vanadium high-speed steel and finished with a steam oxide coating, this tap runs in a right-hand direction with a 45-degree helix angle and two flutes. The H5 thread limit holds tight tolerances suitable for precision threading applications. Thread size is 4-40 UNC with a 0.197-inch thread length and an overall length of 1.875 inches. Licensed machinists and tool-and-die professionals use this tap where chip evacuation toward the shank is needed in short, confined bores.

This tap is suited for threading stainless steel, high-carbon steel, low-carbon steel, and medium-carbon steel workpieces. The bottoming chamfer style makes it the correct choice when threads must extend to within one or two pitches of the bottom of a blind hole. Series 303 from OSG targets general-purpose precision tapping in both production and maintenance environments. The small shank diameter of approximately 0.141 inches fits standard tap holders and collet chucks for #4 machine screw taps.

Key Features

• Bottoming chamfer provides thread engagement near the bottom of blind holes
• 45-degree right-hand spiral flute directs chips toward the shank for cleaner blind-hole tapping
• Vanadium high-speed steel construction improves wear resistance and edge retention
• Steam oxide coating reduces friction and provides light corrosion resistance during storage and use
• H5 thread limit maintains close tolerance control for precise thread fits
• Right-hand thread, right-hand flute — no reverse-cutting confusion on standard setups

Compatibility

Designed for cutting 4-40 UNC internal threads in stainless steel, high-carbon steel, low-carbon steel, and medium-carbon steel. Fits standard tap holders, collet chucks, and tapping heads sized for #4 machine screw taps.

Installation Notes

This tap should be installed by a machinist or qualified tool operator familiar with thread-cutting speeds, feeds, and cutting fluid requirements for the workpiece material. Always secure the workpiece completely before tapping and use an appropriate cutting fluid or tapping compound for the material being threaded. Ensure the tap is aligned perpendicular to the workpiece surface before engagement to avoid tap breakage, which is especially critical with small-diameter taps in this size range. Do not apply excessive axial force — allow the tap to follow its own lead.